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wWCI`,SF*7$$\"3b'e&*\\&R8+?F*$\"34(GEz$e`,SF*7$$\"3?i#=$eY8+?F*$\"3C6f
S^'Q&**RF*7$$\"3'y$4kh`8+?F*$\"31Dl)[YT&**RF*7$$\"3*RMA#))49+?F*$\"35b
qwsRc**RF*7$$\"36]P![hY,+#F*$\"3i,4r!['e**RF*7$$\"3-U5FEn:+?F*$\"3;#HZ
'Hpi**RF*7$$\"3[L$Qx$o;+?F*$\"3Ol\")yytm**RF*7$$\"3N+v.I%)=+?F*$\"3k!)
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[9uE?$)**RF*7$$\"3r5PyK$4-+#F*$\"33d]&\\PP)**RF*7$$\"3GIwpp1@+?F*$\"3m
UAM&=+%F*7$$\"3B2LN+%F*7$$\"3Lzp%*\\%R-+#F*$\"3s%>Cr&y&>+%F*7$$\"3Se9S8&\\-
+#F*$\"3KrF'e6)*>+%F*7$$\"3>D1#=bq-+#F*$\"3^)y![!G#3-SF*7$$\"3&RUB@+%F*7$$\"3fL3s?6H+?F*$\"3:4YjnX;-SF*7$$\"3zn*\\Oz\"H+?
F*$\"3\"[SV(fs;+SF*7$$\"3a,\"zlY#H+?F*$\"3J0J&=&*p,+%F*7$$\"3tN#3&RJH+
?F*$\"3`8P'Rks,+%F*7$$\"3#*ptV7QH+?F*$\"3oF_2O`<+SF*7$$\"3JQcHe^H+?F*$
\"30s4I?2=+SF*7$$\"3q1R:/lH+?F*$\"3HR.`/h=+SF*7$$\"3.V/(e>*H+?F*$\"3kS
***H(o>+SF*7$$\"3Nzpe()=I+?F*$\"3jKS[Tw?+SF*7$$\"3,_+-rsI+?F*$\"3g(o&
\\y\"H-+%F*7$$\"37DJXaEJ+?F*$\"3(oIlbr]-+%F*7$$\"3s&*[ACIK+?F*$\"3zKUC
,AH+SF*7$$\"3wmm*RRL.+#F*$\"3,C#QroL.+%F*7$$\"3%=/'e)*RM+?F*$\"38%>zE6
w.+%F*7$$\"3\"pTvJga.+#F*$\"3Wz]WQ&=/+%F*7$$\"3OFWch)f.+#F*$\"3ka!eddR
/+%F*7$$\"3!yV`*>^O+?F*$\"3RJj781Y+SF*7$$\"3>!p]XVm.+#F*$\"36SqZseY+SF
*7$$\"3-Vz9\\xO+?F*$\"3R27$=8r/+%F*7$$\"3mplW1%o.+#F*$\"3A)e4:wt/+%F*7
$$\"3&e>XP1p.+#F*$\"3ZJ))=\"Rw/+%F*7$$\"30AQ/@(p.+#F*$\"3.Q*o3-z/+%F*7
$$\"3C[CMy.P+?F*$\"3X4*\\0l\"[-SF*7$$\"3Y`p`2IP+?F*$\"37PCGp@\\-SF*7$$
\"3oe9tOcP+?F*$\"3G*yG!)o-D+%F*7$$\"3]H#e0I&Q+?F*$\"3GQ%*o]8a-SF*7$$\"
3J+]Qk\\R+?F*$\"3xmo`8+e-SF*7$$\"3h$3dg6+#F*$\"35ST@Q'oE+%F*7$$\"3?v
oTAqU+?F*$\"3sXc,s#3F+%F*7$$\"3zmmxGpV+?F*$\"3nBM,1zu-SF*7$$\"39J&**)4
AW+?F*$\"34?x9N!pF+%F*7$$\"3%fRA5\\Z/+#F*$\"3W*zPV;!z-SF*7$$\"3(Qvi6:[
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F*$\"3O/vAe=#3+%F*7$$\"34D\"oK0e/+#F*$\"3]'H&)GUK3+%F*7$$\"3F+]oi\"o/+
#F*$\"34+j\"*pG(3+%F*7$$\"3,v=5s#y/+#F*$\"3%Gq^rJ84+%F*7$$\"3<+++++]+?
F*$\"3f+++]-+,SF*-%'COLOURG6&%$RGBG$\"#5!\"\"$\"\"!FegnFdgn-%+AXESLABE
LSG6$Q\"x6\"Q!Fjgn-%%VIEWG6$;$\"&&**>!\"%$\"&0+#Fbhn%(DEFAULTG" 1 2 0
1 10 0 2 9 1 4 2 1.000000 45.000000 44.000000 0 0 "Curve 1" }}}}{PARA
0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";"
}}}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 41 "More examples of discontinuou
s functions " }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}{SECT
1 {PARA 4 "" 0 "" {TEXT -1 10 "Example 1 " }}{PARA 0 "" 0 "" {TEXT -1
0 "" }}{PARA 0 "" 0 "" {TEXT -1 24 "The function f given by " }
{XPPEDIT 18 0 "f(x) = x+abs(x)/x;" "6#/-%\"fG6#%\"xG,&F'\"\"\"*&-%$abs
G6#F'F)F'!\"\"F)" }{TEXT -1 24 " has a discontinuity at " }{XPPEDIT
18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 15 ". The value of " }{XPPEDIT
18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 14 " are close to " }{XPPEDIT
18 0 "-1" "6#,$\"\"\"!\"\"" }{TEXT -1 6 " when " }{TEXT 267 1 "x" }
{TEXT -1 53 " is close to 0 and negative, but jump to values close" }
{XPPEDIT 18 0 " ``+1" "6#,&%!G\"\"\"F%F%" }{TEXT -1 4 " as " }{TEXT
268 1 "x" }{TEXT -1 59 " increases through 0 to take positive values c
lose to zero." }}{PARA 0 "" 0 "" {TEXT -1 22 "For example, f(-0.001)"
}{XPPEDIT 18 0 "`` = -1.001;" "6#/%!G,$-%&FloatG6$\"%,5!\"$!\"\"" }
{TEXT -1 16 ", while f(0.001)" }{XPPEDIT 18 0 "``=1.001" "6#/%!G-%&Flo
atG6$\"%,5!\"$" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 67 "f := x -> x+abs(x)/x:\n'f(x)
'=f(x);\nplot(f(x),x=-3..3,discont=true);" }}{PARA 11 "" 1 ""
{XPPMATH 20 "6#/-%\"fG6#%\"xG,&F'\"\"\"*&-%$absGF&F)F'!\"\"F)" }}
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$\"3YjZ.X!=wN%Ffu$\"3NwM]/=wN9F07$$\"3O\")=wV#fS*\\Ffu$\"39)=wV#fS*\\
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0+#F0$\"3At*)*p@80+$F07$$\"3y>%pV6!Hl?F0$\"3y>%pV6!HlIF07$$\"3hCq76w)R
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Kvj@OtBF0$\"3evKvj@OtLF07$$\"39t!*\\gL'zV#F0$\"39t!*\\gL'zV$F07$$\"37O
'**4*>=+DF0$\"37O'**4*>=+NF07$$\"3'3QAr_4Qc#F0$\"3'3QAr_4Qc$F07$$\"3uz
67&>5pi#F0$\"3uz67&>5pi$F07$$\"3!Q@Ic:$*[o#F0$\"3!Q@Ic:$*[o$F07$$\"3i.
tur\"[8v#F0$\"3i.tur\"[8v$F07$$\"32F%y.L'y5GF0$\"32F%y.L'y5QF07$$\"3_!
oEY!)fT(GF0$\"3_!oEY!)fT(QF07$$\"3Mn`v0j\"[$HF0$\"3Mn`v0j\"[$RF07$$\"
\"$F*$\"\"%F*-%'COLOURG6&%$RGBG$\"*++++\"!\")$F*F*Fhjl-%+AXESLABELSG6$
Q\"x6\"Q!F][m-%%VIEWG6$;F(F]jl%(DEFAULTG" 1 2 0 1 10 0 2 9 1 4 2
1.000000 45.000000 45.000000 0 0 "Curve 1" }}}}{EXCHG {PARA 0 "> " 0 "
" {MPLTEXT 1 0 1 ";" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "
" {TEXT -1 9 "The term " }{XPPEDIT 18 0 "abs(x)/x" "6#*&-%$absG6#%\"xG
\"\"\"F'!\"\"" }{TEXT -1 22 " has the value 1 when " }{TEXT 269 1 "x"
}{TEXT -1 17 " is positive and " }{XPPEDIT 18 0 "-1" "6#,$\"\"\"!\"\"
" }{TEXT -1 6 " when " }{TEXT 270 1 "x" }{TEXT -1 14 " is negative. "
}{XPPEDIT 18 0 "abs(x)/x" "6#*&-%$absG6#%\"xG\"\"\"F'!\"\"" }{TEXT -1
21 " is not defined when " }{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }
{TEXT -1 42 " since it gives the meaningless exression " }{XPPEDIT 18
0 "0/0" "6#*&\"\"!\"\"\"F$!\"\"" }{TEXT -1 2 ". " }}{PARA 0 "" 0 ""
{TEXT -1 14 "Indeed, since " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }
{XPPEDIT 18 0 "abs(x) = PIECEWISE([x, 0 <= x],[-x, x < 0]);" "6#/-%$ab
sG6#%\"xG-%*PIECEWISEG6$7$F'1\"\"!F'7$,$F'!\"\"2F'F-" }{TEXT -1 2 ", \+
" }}{PARA 0 "" 0 "" {TEXT -1 16 "it follows that " }}{PARA 257 "" 0 "
" {TEXT -1 1 " " }{XPPEDIT 18 0 "abs(x)/x = PIECEWISE([1, 0 < x],[unde
fined, x = 0],[-1, x < 0]);" "6#/*&-%$absG6#%\"xG\"\"\"F(!\"\"-%*PIECE
WISEG6%7$F)2\"\"!F(7$%*undefinedG/F(F07$,$F)F*2F(F0" }{TEXT -1 2 ". "
}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 18 "The mid
dle line, \"" }{TEXT 273 9 "undefined" }{TEXT -1 5 " " }{XPPEDIT
18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 13 "\", in this " }{TEXT 261
17 "piecewise formula" }{TEXT -1 45 " is included for emphasis, but ca
n be omitted" }}{PARA 0 "" 0 "" {TEXT -1 6 "Hence " }{XPPEDIT 18 0 "f(
x)" "6#-%\"fG6#%\"xG" }{TEXT -1 54 " can be described by the following
piecewise formula: " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18
0 "f(x)=PIECEWISE([x+1,x>0],[undefined, x = 0],[x-1,x<0])" "6#/-%\"fG6
#%\"xG-%*PIECEWISEG6%7$,&F'\"\"\"F-F-2\"\"!F'7$%*undefinedG/F'F/7$,&F'
F-F-!\"\"2F'F/" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 54 "Again,
the middle line is only included for emphasis. " }}{PARA 0 "" 0 ""
{TEXT -1 13 "The graph of " }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }
{TEXT -1 53 " therefore consists of the part of the infinite line " }
{XPPEDIT 18 0 "y=x+1" "6#/%\"yG,&%\"xG\"\"\"F'F'" }{TEXT -1 32 " which
lies to the right of the " }{TEXT 271 1 "y" }{TEXT -1 41 " axis toget
her with the part of the line " }{XPPEDIT 18 0 "y=x-1" "6#/%\"yG,&%\"x
G\"\"\"F'!\"\"" }{TEXT -1 31 " which lies to the left of the " }{TEXT
272 1 "y" }{TEXT -1 62 " axis. The graph consists of these two \"half-
lines\" or \"rays\"." }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA
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vely closer to " }{XPPEDIT 18 0 "-1" "6#,$\"\"\"!\"\"" }{TEXT -1 4 " a
s " }{TEXT 274 1 "x" }{TEXT -1 67 " approaches 0 from the left (throug
h values less than 0), so that: " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }
{XPPEDIT 18 0 "Limit(f(x),x = 0^`-`) = -1;" "6#/-%&LimitG6$-%\"fG6#%\"
xG/F*)\"\"!%\"-G,$\"\"\"!\"\"" }{TEXT -1 1 " " }}{PARA 0 "" 0 ""
{TEXT -1 33 "On the other hand, the values of " }{XPPEDIT 18 0 "f(x)"
"6#-%\"fG6#%\"xG" }{TEXT -1 37 " become progressively closer to 1 as \+
" }{TEXT 275 1 "x" }{TEXT -1 71 " approaches 0 from the right (through
values greater than 0), so that: " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "Limit(f(x),x = 0^`+`)
= 1;" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*)\"\"!%\"+G\"\"\"" }{TEXT -1 2 "
. " }}{PARA 0 "" 0 "" {TEXT 261 4 "Note" }{TEXT -1 11 ": Although " }
{XPPEDIT 18 0 "f(x)=x+abs(x)/x" "6#/-%\"fG6#%\"xG,&F'\"\"\"*&-%$absG6#
F'F)F'!\"\"F)" }{TEXT -1 21 " is discontinuous at " }{XPPEDIT 18 0 "x=
0" "6#/%\"xG\"\"!" }{TEXT -1 49 ", it is continuous at all non-zero re
al numbers. " }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}}{SECT
1 {PARA 4 "" 0 "" {TEXT -1 10 "Example 2 " }}{PARA 0 "" 0 "" {TEXT -1
24 "The function f given by " }{XPPEDIT 18 0 "f(x) = x/(x-1);" "6#/-%
\"fG6#%\"xG*&F'\"\"\",&F'F)F)!\"\"F+" }{TEXT -1 24 " has a discontinui
ty at " }{XPPEDIT 18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 2 ". " }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 3 "As " }
{TEXT 276 1 "x" }{TEXT -1 72 " approaches 1 from the left (through val
ues less than 1), the numerator " }{TEXT 280 1 "x" }{TEXT -1 4 " of "
}{XPPEDIT 18 0 "f(x)=x/(x-1)" "6#/-%\"fG6#%\"xG*&F'\"\"\",&F'F)F)!\"\"
F+" }{TEXT -1 37 " approaches 1, while the denominator " }{XPPEDIT 18
0 "x-1" "6#,&%\"xG\"\"\"F%!\"\"" }{TEXT -1 71 " approaches 0 from the \+
left (through negative values). It follows that " }{XPPEDIT 18 0 "f(x)
" "6#-%\"fG6#%\"xG" }{TEXT -1 45 " takes progressively larger negative
values (" }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 34 " appr
oaches negative infinity) as " }{TEXT 278 1 "x" }{TEXT -1 14 " approac
hes 1 " }{TEXT 261 13 "from the left" }{TEXT -1 11 ", so that: " }}
{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "Limit(f(x),x = 1^`-`)
= -infinity;" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*)\"\"\"%\"-G,$%)infinity
G!\"\"" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 ""
0 "" {TEXT -1 80 "This can be checked empirically by numerical calcula
tions. For example, f(0.999)" }{XPPEDIT 18 0 "``=-999" "6#/%!G,$\"$***
!\"\"" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 29 "This means that
the graph of " }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 35 "
approaches the vertical asymptote " }{XPPEDIT 18 0 "x=1" "6#/%\"xG\"
\"\"" }{TEXT -1 34 " \"going downwards from the left\". " }}{PARA 0 "
" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 3 "As " }{TEXT 281 1 "
x" }{TEXT -1 14 " approaches 1 " }{TEXT 261 14 "from the right" }
{TEXT -1 48 " (through values greater than 1), the numerator " }{TEXT
285 1 "x" }{TEXT -1 4 " of " }{XPPEDIT 18 0 "f(x)=x/(x-1)" "6#/-%\"fG6
#%\"xG*&F'\"\"\",&F'F)F)!\"\"F+" }{TEXT -1 37 " approaches 1, while th
e denominator " }{XPPEDIT 18 0 "x-1" "6#,&%\"xG\"\"\"F%!\"\"" }{TEXT
-1 72 " approaches 0 from the right (through positive values). It foll
ows that " }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 45 " take
s progressively larger positive values (" }{XPPEDIT 18 0 "f(x)" "6#-%
\"fG6#%\"xG" }{TEXT -1 25 " approaches infinity) as " }{TEXT 283 1 "x
" }{TEXT -1 14 " approaches 1 " }{TEXT 261 14 "from the right" }{TEXT
-1 11 ", so that: " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0
"Limit(f(x),x = 1^`+`) = infinity;" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*)\"
\"\"%\"+G%)infinityG" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "
" }}{PARA 0 "" 0 "" {TEXT -1 72 "This can be checked empirically by nu
merical calculations. For example, " }{XPPEDIT 18 0 "f(1.0001) = 10001
;" "6#/-%\"fG6#-%&FloatG6$\"&,+\"!\"%F*" }{TEXT -1 2 ". " }}{PARA 0 "
" 0 "" {TEXT -1 29 "This means that the graph of " }{XPPEDIT 18 0 "f(x
)" "6#-%\"fG6#%\"xG" }{TEXT -1 35 " approaches the vertical asymptote \+
" }{XPPEDIT 18 0 "x=1" "6#/%\"xG\"\"\"" }{TEXT -1 33 " \"going upwards
from the right\". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "
" {TEXT -1 13 "The graph of " }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG"
}{TEXT -1 19 " also has the line " }{XPPEDIT 18 0 "y=1" "6#/%\"yG\"\"
\"" }{TEXT -1 113 " as a horizontal asymptote, although this is not pe
rtinent to the question of continuity. To see this note that" }}
{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "f(x)=1+1/(x-1)" "6#/-
%\"fG6#%\"xG,&\"\"\"F)*&F)F),&F'F)F)!\"\"F,F)" }{TEXT -1 2 ". " }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 20 "This expr
ession for " }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 52 " ca
n be obtained the following polynomial division. " }}{PARA 257 "" 0 "
" {TEXT -1 27 " 1" }}{PARA 257 "" 0 "" {TEXT
-1 24 " ______" }}{PARA 257 "" 0 "" {TEXT -1 1 " " }
{XPPEDIT 18 0 "x-1" "6#,&%\"xG\"\"\"F%!\"\"" }{TEXT -1 5 " | " }
{TEXT 286 1 "x" }{TEXT -1 1 " " }}{PARA 257 "" 0 "" {TEXT -1 20 " \+
" }{XPPEDIT 18 0 "x-1" "6#,&%\"xG\"\"\"F%!\"\"" }{TEXT
-1 1 " " }}{PARA 257 "" 0 "" {TEXT -1 24 " _____" }}
{PARA 257 "" 0 "" {TEXT -1 26 " 1" }}{PARA 0 "
" 0 "" {TEXT -1 3 "As " }{TEXT 287 1 "x" }{TEXT -1 76 " gets progressi
vely larger in the positive direction (approaches infinity), " }
{XPPEDIT 18 0 "1/(x-1)" "6#*&\"\"\"F$,&%\"xGF$F$!\"\"F'" }{TEXT -1 40
" approaches 0 (from the right), so that " }{XPPEDIT 18 0 "f(x)=1+1/(x
-1)" "6#/-%\"fG6#%\"xG,&\"\"\"F)*&F)F),&F'F)F)!\"\"F,F)" }{TEXT -1 43
" approaches 1 (from the right), in symbols " }{XPPEDIT 18 0 "f(x)->1
" "6#f*6#-%\"fG6#%\"xG7\"6$%)operatorG%&arrowG6\"\"\"\"F-F-F-" }
{XPPEDIT 18 0 "``^`+`" "6#)%!G%\"+G" }{TEXT -1 5 ", as " }{XPPEDIT 18
0 "x->infinity" "6#f*6#%\"xG7\"6$%)operatorG%&arrowG6\"%)infinityGF*F*
F*" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 1 " " }}{PARA 0 "" 0 "
" {TEXT -1 3 "As " }{TEXT 288 1 "x" }{TEXT -1 85 " gets progressively \+
larger in the negative direction (approaches negative infinity), " }
{XPPEDIT 18 0 "1/(x-1)" "6#*&\"\"\"F$,&%\"xGF$F$!\"\"F'" }{TEXT -1 39
" approaches 0 (from the left), so that " }{XPPEDIT 18 0 "f(x)=1+1/(x-
1)" "6#/-%\"fG6#%\"xG,&\"\"\"F)*&F)F),&F'F)F)!\"\"F,F)" }{TEXT -1 42 "
approaches 1 (from the left), in symbols " }{XPPEDIT 18 0 "f(x)->1" "
6#f*6#-%\"fG6#%\"xG7\"6$%)operatorG%&arrowG6\"\"\"\"F-F-F-" }{XPPEDIT
18 0 "``^`-`;" "6#)%!G%\"-G" }{TEXT -1 5 ", as " }{XPPEDIT 18 0 "x->-i
nfinity" "6#f*6#%\"xG7\"6$%)operatorG%&arrowG6\",$%)infinityG!\"\"F*F*
F*" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 1 " " }}{PARA 0 "" 0 "
" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 184 "f := x ->
x/(x-1):\n'f(x)'=f(x);\np1 := plot(f(x),x=-3..5,y=-3..5,discont=true,
thickness=2):\np2 := plot([[[-3,1],[5,1]],[[1,-3],[1,5]]],color=black,
linestyle=3):\nplots[display]([p1,p2]);" }}{PARA 11 "" 1 "" {XPPMATH
20 "6#/-%\"fG6#%\"xG*&F'\"\"\",&F'F)F)!\"\"F+" }}{PARA 13 "" 1 ""
{GLPLOT2D 339 306 306 {PLOTDATA 2 "6'-%'CURVESG6&7gn7$$!\"$\"\"!$\"3++
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F-7$$!3`80j^5*H\">F1$\"3=)palR-rc'F-7$$!3zPdvJ\"3&H=F1$\"3OEReOo\"eY'F
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3Q()ey[h=(e\"F1$\"3o<&p+(ozMhF-7$$!3knCvH\\N)\\\"F1$\"3at&fW:mt*fF-7$$
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Y]#F17$$\"3k-9Qpb
59>F1$\"3qP)[yalR4#F17$$\"3v\\!*\\P,Q+?F1$\"3kd0&p+?'**>F17$$\"3qxCGd*
3q3#F1$\"3V**pp?c&*>>F17$$\"3AqP2x=\\q@F1$\"3ol;$GoTV&=F17$$\"3]540mBI
YAF1$\"3:>\\\"o]tB!=F17$$\"3s7A**p$[kL#F1$\"39!=#)f(=D[0Oy*e
C$F1$\"3g3eYGiDX9F17$$\"3?76Y%)Qr0S\"F17$$\"3'>&Q`=#f
ke$F1$\"3'o,2a%*GmQ\"F17$$\"3eb\\mc4NnOF1$\"3sucS'z.\\P\"F17$$\"3i*p:J
:?Pv$F1$\"3GWm72^9j8F17$$\"3-3n3#[$)>$QF1$\"3'QWxTS4JN\"F17$$\"3DNhqsf
aQ$3O0)*RF1$\"3?QsZR(\\NL\"F17$$\"3q\"[%z%
G2A3%F1$\"3>B%RC\"GWC8F17$$\"3IE@U&)G[kTF1$\"3bUk;(R2gJ\"F17$$\"3)eXtV
\"yh]UF1$\"3tqv]FQj28F17$$\"3RFFL))fdLVF1$\"3)ztRE;y**H\"F17$$\"3]N17.
FT=WF1$\"3'zQ*)>VLDH\"F17$$\"3\"p'p2Fpa-XF1$\"3UCj[Cl]&G\"F17$$\"3-d.0
Tv&)zXF1$\"3ofZuC2Mz7F17$$\"3'HH28A$[F1$\"3APr]Ce%4E\"F17$$\"3tysr2%)3
8\\F1$\"3qjuI@Ebb7F17$$\"\"&F*$\"3+++++++]7F1-%'COLOURG6&%$RGBG$\"*+++
+\"!\")$F*F*F_am-%*THICKNESSG6#\"\"#-F$6%7$7$F($\"\"\"F*7$Fd`mFham-Fi`
m6&F[amF*F*F*-%*LINESTYLEG6#\"\"$-F$6%7$7$FhamF(7$FhamFd`mF[bmF]bm-%+A
XESLABELSG6%Q\"x6\"Q\"yFjbm-%%FONTG6#%(DEFAULTG-%%VIEWG6$;F(Fd`mFccm"
1 2 0 1 10 0 2 9 1 4 2 1.000000 45.000000 45.000000 0 0 "Curve 1" "Cur
ve 2" "Curve 3" }}}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 28 "When foll
owing the graph of " }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT
-1 51 " from left to right (or in taking sample values of " }{XPPEDIT
18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 4 " as " }{TEXT 289 1 "x" }
{TEXT -1 27 " increases), the values of " }{XPPEDIT 18 0 "f(x)" "6#-%
\"fG6#%\"xG" }{TEXT -1 63 " \"jump\" from large negative values to lar
ge positive values as " }{TEXT 290 1 "x" }{TEXT -1 22 " increases thro
ugh 1. " }}{PARA 0 "" 0 "" {TEXT -1 21 "Indeed the values of " }
{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 33 " obtained by the \+
Maple procedure " }{TEXT 0 4 "plot" }{TEXT -1 26 " exhibit this phenom
enon. " }}{PARA 0 "" 0 "" {TEXT -1 27 "The last point obtained by " }
{TEXT 0 4 "plot" }{TEXT -1 4 " as " }{TEXT 291 1 "x" }{TEXT -1 60 " ap
proaches 1 from the left and the first point obtained by " }{TEXT 0 4
"plot" }{TEXT -1 7 " after " }{XPPEDIT 18 0 "x=1" "6#/%\"xG\"\"\"" }
{TEXT -1 16 " are as follows." }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 145 "plot(f(x),x=-3..5,y=-3..5,t
hickness=2):\npts := op(1,op(1,%)):\nfor ct to nops(pts) do if pts[ct,
1]>1 then break end if end do:\npts[ct-1];\npts[ct];" }}{PARA 11 "" 1
"" {XPPMATH 20 "6#7$$\"3gKLLLG^g**!#=$!3Equpa$oC_#!#:" }}{PARA 11 ""
1 "" {XPPMATH 20 "6#7$$\"3I$3x19j:+\"!#<$\"3FO2CioP2k!#:" }}}{PARA 0 "
" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 13 "When option \"" }
{TEXT 262 12 "discont=true" }{TEXT -1 15 "\" is used with " }{TEXT 0
4 "plot" }{TEXT -1 69 ", the two branches are plotted separately and t
he last point with an " }{TEXT 292 1 "x" }{TEXT -1 60 " coordinate les
s than 1 followed by the first point with an " }{TEXT 293 1 "x" }
{TEXT -1 35 " coordinate greater than 1 are ... " }}{PARA 0 "" 0 ""
{TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 115 "plot(f(x),x
=-3..5,y=-3..5,discont=true,thickness=2):\nop(1,ListTools[Reverse](op(
1,op(1,%))));\nop(1,op(2,op(1,%%)));" }}{PARA 11 "" 1 "" {XPPMATH 20 "
6#7$$\"2%******R********!#<$!3KiT7Ummm;!\"*" }}{PARA 11 "" 1 ""
{XPPMATH 20 "6#7$$\"3%*******4+++5!#<$\"33ru2;+++5!\"*" }}}{PARA 0 ""
0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 90 "These points do not \+
appear in the previous graph because of the restriction placed on the \+
" }{TEXT 294 1 "y" }{TEXT -1 11 " variable. " }}{PARA 0 "" 0 "" {TEXT
-1 0 "" }}{PARA 0 "" 0 "" {TEXT 261 4 "Note" }{TEXT -1 11 ": Although \+
" }{XPPEDIT 18 0 "f(x) = x/(x-1);" "6#/-%\"fG6#%\"xG*&F'\"\"\",&F'F)F)
!\"\"F+" }{TEXT -1 21 " is discontinuous at " }{XPPEDIT 18 0 "x=1" "6#
/%\"xG\"\"\"" }{TEXT -1 46 ", it is continuous at all other real numbe
rs. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 ""
{MPLTEXT 1 0 1 ";" }}}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 10 "Example 3 \+
" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 35 "Consi
der the function f defined by " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }
{XPPEDIT 18 0 "f(x)=``" "6#/-%\"fG6#%\"xG%!G" }{TEXT -1 20 "the greate
st integer" }{XPPEDIT 18 0 "``<=x" "6#1%!G%\"xG" }{TEXT -1 2 ". " }}
{PARA 0 "" 0 "" {TEXT -1 61 "We could use double square brackets to de
note this function. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "
" {TEXT -1 18 "Thus, for example," }}{PARA 257 "" 0 "" {TEXT -1 1 " "
}{XPPEDIT 18 0 "f(Pi) = [[Pi]];" "6#/-%\"fG6#%#PiG7#7#F'" }{XPPEDIT
18 0 "``=3" "6#/%!G\"\"$" }{TEXT -1 3 ", " }{XPPEDIT 18 0 "f(sqrt(101
))=[[sqrt(101)]]" "6#/-%\"fG6#-%%sqrtG6#\"$,\"7#7#-F(6#F*" }{XPPEDIT
18 0 "``=10" "6#/%!G\"#5" }{TEXT -1 3 ", " }{XPPEDIT 18 0 "f(-Pi)=[[-
Pi]]" "6#/-%\"fG6#,$%#PiG!\"\"7#7#,$F(F)" }{XPPEDIT 18 0 "``=-4" "6#/%
!G,$\"\"%!\"\"" }{TEXT -1 1 "," }}{PARA 257 "" 0 "" {TEXT -1 1 " " }
{XPPEDIT 18 0 "f(56+10^(-100))=[[56+10^(-100)]]" "6#/-%\"fG6#,&\"#c\"
\"\")\"#5,$\"$+\"!\"\"F)7#7#,&F(F))F+,$F-F.F)" }{XPPEDIT 18 0 "``=56"
"6#/%!G\"#c" }{TEXT -1 3 ", " }{XPPEDIT 18 0 "f(56-10^(-100)) = [[56-
10^(-100)]];" "6#/-%\"fG6#,&\"#c\"\"\")\"#5,$\"$+\"!\"\"F.7#7#,&F(F))F
+,$F-F.F." }{XPPEDIT 18 0 "``=55" "6#/%!G\"#b" }{TEXT -1 2 ". " }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 1 " " }}
{PARA 0 "" 0 "" {TEXT -1 42 "The value jumps up from one integer value
" }{XPPEDIT 18 0 "n-1" "6#,&%\"nG\"\"\"F%!\"\"" }{TEXT -1 21 " to the
next integer " }{TEXT 299 1 "n" }{TEXT -1 4 " as " }{TEXT 297 1 "x" }
{TEXT -1 37 " increases through the integer value " }{TEXT 298 1 "n" }
{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 33 "More precisely, for eac
h integer " }{TEXT 300 1 "n" }{TEXT -1 1 "," }}{PARA 257 "" 0 ""
{TEXT -1 1 " " }{XPPEDIT 18 0 "f(x)=[[x]]" "6#/-%\"fG6#%\"xG7#7#F'" }
{XPPEDIT 18 0 "`` = n-1;" "6#/%!G,&%\"nG\"\"\"F'!\"\"" }{TEXT -1 7 " \+
for " }{XPPEDIT 18 0 "n-1<=x" "6#1,&%\"nG\"\"\"F&!\"\"%\"xG" }
{XPPEDIT 18 0 "`` " 0 "" {MPLTEXT 1 0
289 "p1 := plot([[seq([i,i],i=-6..6)]$3],style=point,color=red,symbol=
[circle,diamond,cross]):\np2 := plot([seq([i,i-1],i=-5..6)],style=poin
t,color=red,symbol=circle):\np3 := plot(floor(x),x=-6..6,color=red,dis
cont=true,thickness=2):\nplots[display]([p1,p2,p3],labels=[`x`,`y`],ti
tle=`y = [[x]]`);" }}{PARA 13 "" 1 "" {GLPLOT2D 476 476 476 {PLOTDATA
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$$\"336_m))RRLeFfpFI7$$\"3?!>1p;.Y&eFfpFI7$$\"37_IWAnjveFfpFI7$$\"3;b3
_vV'\\*eFfpFI7$$\"3oZD2Zg6 " 0 "" {MPLTEXT 1 0 1 ";" }}}}
{SECT 1 {PARA 4 "" 0 "" {TEXT -1 9 "Example 4" }}{PARA 0 "" 0 ""
{TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 35 "Consider the function f d
efined by " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "f(x) = \+
(-1)^[[x]];" "6#/-%\"fG6#%\"xG),$\"\"\"!\"\"7#7#F'" }{TEXT -1 2 ". " }
}{PARA 0 "" 0 "" {TEXT -1 1 " " }}{PARA 0 "" 0 "" {TEXT -1 1 " " }
{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 17 " jumps from 1 to \+
" }{XPPEDIT 18 0 "-1;" "6#,$\"\"\"!\"\"" }{TEXT -1 4 " as " }{TEXT
302 1 "x" }{TEXT -1 42 " increases through each odd integer, and " }
{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 12 " jumps from " }
{XPPEDIT 18 0 "-1" "6#,$\"\"\"!\"\"" }{TEXT -1 9 " to 1 as " }{TEXT
303 1 "x" }{TEXT -1 37 " increases through each even integer." }}
{PARA 0 "" 0 "" {TEXT -1 16 "More precisely, " }}{PARA 257 "" 0 ""
{TEXT -1 1 " " }{XPPEDIT 18 0 "f(x)=PIECEWISE([1, `if`* n<=x and x " 0 "" {MPLTEXT 1 0 360 "p1 :
= plot([[seq([2*i,1],i=-3..3),seq([2*i-1,-1],i=-2..3)]$3],style=point,
\n color=red,symbol=[circle,diamond,cross]):\np2 := plot([seq([2*i-1,
1],i=-2..3),seq([2*i,-1],i=-2..3)],style=point,\n color=red,symbol=ci
rcle):\np3 := plot((-1)^floor(x),x=-6..6,color=red,discont=true,thickn
ess=2):\nplots[display]([p1,p2,p3],labels=[`x`,`y`],view=-1.9..1.9,yti
ckmarks=3);" }}{PARA 13 "" 1 "" {GLPLOT2D 579 184 184 {PLOTDATA 2 "6+-
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-1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 139 "The function f is discontinuou
s at every integer, but is continuous everywhere else, that is, at all
real numbers that are not integers. . " }}{PARA 0 "" 0 "" {TEXT -1 0
"" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}}{EXCHG {PARA 0 ">
" 0 "" {MPLTEXT 1 0 1 ";" }}}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 68 "Br
eaking down the checking of continuity of a function f at a point " }
{XPPEDIT 18 0 "x=a" "6#/%\"xG%\"aG" }{TEXT -1 13 " into 3 steps" }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 51 "As sugges
ted in the first section, a function f is " }{TEXT 261 10 "continuous
" }{TEXT -1 4 " at " }{XPPEDIT 18 0 "x=a" "6#/%\"xG%\"aG" }{TEXT -1
16 " provided that: " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18
0 "Limit(f(x),x = a)=f(a)" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*%\"aG-F(6#F,
" }{TEXT -1 14 " ------- (i). " }}{PARA 0 "" 0 "" {TEXT -1 76 "Note th
at there are three steps involved in checking that f is continuous a \+
" }{XPPEDIT 18 0 "x=a" "6#/%\"xG%\"aG" }{TEXT -1 2 ". " }}{PARA 15 ""
0 "" {TEXT -1 18 " f is defined at " }{XPPEDIT 18 0 "x=a" "6#/%\"xG%
\"aG" }{TEXT -1 11 ", that is, " }{TEXT 304 1 "a" }{TEXT -1 84 " belon
gs to the domain of f. This ensures that the right-hand side of (i) \+
exists. " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "Limit(f(x),x = a)" "6#-%&L
imitG6$-%\"fG6#%\"xG/F)%\"aG" }{TEXT -1 73 " exists (as a finite real \+
number). \nFor this to hold both the left limit " }{XPPEDIT 18 0 "Limi
t(f(x),x = a^`-`)" "6#-%&LimitG6$-%\"fG6#%\"xG/F))%\"aG%\"-G" }{TEXT
-1 17 " and right limit " }{XPPEDIT 18 0 "Limit(f(x),x = a^`+`)" "6#-%
&LimitG6$-%\"fG6#%\"xG/F))%\"aG%\"+G" }{TEXT -1 124 " must exist and f
urthermore they must have the same real number value. \nThis ensures t
hat the left-hand side of (i) exists. " }}{PARA 15 "" 0 "" {TEXT -1
94 "Finally, the left and right sides of (i), as obtained in the first
two points, must coincide. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}
{SECT 1 {PARA 4 "" 0 "" {TEXT -1 78 "Checking for continuity with refe
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0 "" {MPLTEXT 1 0 1 ";" }}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 10 "Exampl
e 1 " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 29 "W
e can say that the function " }{XPPEDIT 18 0 "f(x) = x+abs(x)/x;" "6#/
-%\"fG6#%\"xG,&F'\"\"\"*&-%$absG6#F'F)F'!\"\"F)" }{TEXT -1 21 " is dis
continuous at " }{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 16 " si
mply because " }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 19 " \+
is not defined at " }{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 2 "
. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 ""
{MPLTEXT 1 0 162 "f := x -> x+abs(x)/x:\n'f(x)'=f(x);\np1 := plot(f(x)
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ed,symbol=circle):\nplots[display]([p1,p2]);" }}{PARA 11 "" 1 ""
{XPPMATH 20 "6#/-%\"fG6#%\"xG,&F'\"\"\"*&-%$absGF&F)F'!\"\"F)" }}
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defined for all real numbers, in which we give a value at " }
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{TEXT -1 4 "Let " }{XPPEDIT 18 0 "g(x);" "6#-%\"gG6#%\"xG" }{TEXT -1
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iscont=true):\np2 := plot([[0,-1]],style=point,color=red,symbol=circle
):\np3 := plot([[[0,1]]$3],style=point,symbol=[circle,diamond,cross],c
olor=red,symbol=circle):\nplots[display]([p1,p2,p3]);" }}{PARA 11 ""
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"" {TEXT -1 51 "It is intuitively clear that g is discontinuous at " }
{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 10 ", because " }
{XPPEDIT 18 0 "g(x)" "6#-%\"gG6#%\"xG" }{TEXT -1 27 " still \"jumps\" \+
in value as " }{TEXT 305 1 "x" }{TEXT -1 22 " increases through 0. " }
}{PARA 0 "" 0 "" {TEXT -1 31 "We can check for continuity at " }
{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 68 " with reference to t
he 3 step analysis to see whether the condition " }{XPPEDIT 18 0 "Limi
t(g(x),x = 0)=g(0)" "6#/-%&LimitG6$-%\"gG6#%\"xG/F*\"\"!-F(6#F," }
{TEXT -1 8 " holds. " }}{PARA 15 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18
0 "g(0)" "6#-%\"gG6#\"\"!" }{TEXT -1 12 " exists and " }{XPPEDIT 18 0
"g(0)=1" "6#/-%\"gG6#\"\"!\"\"\"" }{TEXT -1 2 ". " }}{PARA 15 "" 0 ""
{XPPEDIT 18 0 "Limit(g(x),x=0)" "6#-%&LimitG6$-%\"gG6#%\"xG/F)\"\"!" }
{TEXT -1 24 " does not exist because " }{XPPEDIT 18 0 "Limit(g(x),x = \+
0^`-`) = -1;" "6#/-%&LimitG6$-%\"gG6#%\"xG/F*)\"\"!%\"-G,$\"\"\"!\"\"
" }{TEXT -1 7 " while " }{XPPEDIT 18 0 "Limit(g(x),x = 0^`+`) = 1;" "6
#/-%&LimitG6$-%\"gG6#%\"xG/F*)\"\"!%\"+G\"\"\"" }{TEXT -1 2 ". " }}
{PARA 15 "" 0 "" {TEXT -1 40 "not applicable because of the 2nd step. \+
" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 11 "There
fore, " }{XPPEDIT 18 0 "g(x)" "6#-%\"gG6#%\"xG" }{TEXT -1 22 " is not \+
continuous at " }{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 2 ". "
}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1
0 1 ";" }}}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 10 "Example 2 " }}{PARA
0 "" 0 "" {TEXT -1 69 "As for the previous example, we can say that th
e function f given by " }{XPPEDIT 18 0 "f(x) = x/(x-1);" "6#/-%\"fG6#%
\"xG*&F'\"\"\",&F'F)F)!\"\"F+" }{TEXT -1 21 " is discontinuous at " }
{XPPEDIT 18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 16 " simply because \+
" }{XPPEDIT 18 0 "f(x)" "6#-%\"fG6#%\"xG" }{TEXT -1 19 " is not define
d at " }{XPPEDIT 18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 2 ". " }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0
184 "f := x -> x/(x-1):\n'f(x)'=f(x);\np1 := plot(f(x),x=-3..5,y=-3..5
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],color=black,linestyle=3):\nplots[display]([p1,p2]);" }}{PARA 11 ""
1 "" {XPPMATH 20 "6#/-%\"fG6#%\"xG*&F'\"\"\",&F'F)F)!\"\"F+" }}{PARA
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{TEXT -1 56 "Now consider the following modification or extension of \+
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!\"\"F+" }{TEXT -1 15 " to a function " }{XPPEDIT 18 0 "g(x)" "6#-%\"g
G6#%\"xG" }{TEXT -1 59 " defined for all real numbers, in which we giv
e a value at " }{XPPEDIT 18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 1 ".
" }}{PARA 0 "" 0 "" {TEXT -1 4 "Let " }{XPPEDIT 18 0 "g(x);" "6#-%\"gG
6#%\"xG" }{TEXT -1 63 " be the functon described by the following pie
cewise formula: " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }}{PARA 257 "" 0
"" {TEXT -1 0 "" }}{PARA 257 "" 0 "" {XPPEDIT 18 0 "g(x) = PIECEWISE([
x/(x-1), x <> 1],[1, x = 1]);" "6#/-%\"gG6#%\"xG-%*PIECEWISEG6$7$*&F'
\"\"\",&F'F-F-!\"\"F/0F'F-7$F-/F'F-" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "
" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 264 "f := x ->
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thickness=2):\np2 := plot([[[-3,1],[5,1]],[[1,-3],[1,5]]],color=black,
linestyle=3):\np3 := plot([[[1,1]]$3],color=red,style=point,symbol=[ci
rcle,diamond,cross]):\nplots[display]([p1,p2,p3]);" }}{PARA 11 "" 1 "
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"" {MPLTEXT 1 0 1 ";" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0
"" {TEXT -1 29 "It is intuitively clear that " }{XPPEDIT 18 0 "g(x)" "
6#-%\"gG6#%\"xG" }{TEXT -1 21 " is discontinuous at " }{XPPEDIT 18 0 "
x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 10 ", because " }{XPPEDIT 18 0 "g(x
)" "6#-%\"gG6#%\"xG" }{TEXT -1 27 " still \"jumps\" in value as " }
{TEXT 306 1 "x" }{TEXT -1 22 " increases through 1. " }}{PARA 0 "" 0 "
" {TEXT -1 31 "We can check for continuity at " }{XPPEDIT 18 0 "x = 1;
" "6#/%\"xG\"\"\"" }{TEXT -1 68 " with reference to the 3 step analysi
s to see whether the condition " }{XPPEDIT 18 0 "Limit(g(x),x = 1) = g
(1);" "6#/-%&LimitG6$-%\"gG6#%\"xG/F*\"\"\"-F(6#F," }{TEXT -1 8 " hold
s. " }}{PARA 15 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "g(1);" "6#-%\"g
G6#\"\"\"" }{TEXT -1 12 " exists and " }{XPPEDIT 18 0 "g(1) = 1;" "6#/
-%\"gG6#\"\"\"F'" }{TEXT -1 2 ". " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "L
imit(g(x),x = 1);" "6#-%&LimitG6$-%\"gG6#%\"xG/F)\"\"\"" }{TEXT -1 24
" does not exist because " }{XPPEDIT 18 0 "Limit(g(x),x = 1^`-`) = -in
finity;" "6#/-%&LimitG6$-%\"gG6#%\"xG/F*)\"\"\"%\"-G,$%)infinityG!\"\"
" }{TEXT -1 8 " while " }{XPPEDIT 18 0 "Limit(g(x),x = 1^`+`) = infin
ity;" "6#/-%&LimitG6$-%\"gG6#%\"xG/F*)\"\"\"%\"+G%)infinityG" }{TEXT
-1 111 ". \nActually, it is sufficient to note that just one of these \+
two one-sided limits is infinite to conclude that " }{XPPEDIT 18 0 "Li
mit(g(x),x = 1)" "6#-%&LimitG6$-%\"gG6#%\"xG/F)\"\"\"" }{TEXT -1 42 " \+
does not exist (as a finite real number)." }}{PARA 15 "" 0 "" {TEXT
-1 40 "not applicable because of the 2nd step. " }}{PARA 0 "" 0 ""
{TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 11 "Therefore, " }{XPPEDIT
18 0 "g(x)" "6#-%\"gG6#%\"xG" }{TEXT -1 22 " is not continuous at " }
{XPPEDIT 18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 2 ". " }}{PARA 0 ""
0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}}
{SECT 1 {PARA 4 "" 0 "" {TEXT -1 10 "Example 3 " }}{PARA 0 "" 0 ""
{TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 89 "Consider the piecewise fu
nction f defined for all real numbers by the piecewise formula: " }}
{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "f(x)=PIECEWISE([x,x<0
],[x^2,0<=x and x<1],[2,1<=x])" "6#/-%\"fG6#%\"xG-%*PIECEWISEG6%7$F'2F
'\"\"!7$*$F'\"\"#31F-F'2F'\"\"\"7$F01F4F'" }{TEXT -1 2 ". " }}{PARA 0
"" 0 "" {TEXT -1 13 "The graph of " }{XPPEDIT 18 0 "y=f(x)" "6#/%\"yG-
%\"fG6#%\"xG" }{TEXT -1 26 " can be drawn as follows. " }}{PARA 0 ""
0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 272 "f := x
-> piecewise(x<0,x,x<1,x^2,2):\n'f(x)'=f(x);\np1 := plot(f(x),x=-3..3
,discont=true,thickness=2):\np2 := plot([[1,1]],style=point,color=red,
symbol=circle):\np3 := plot([[[1,2]]$2],style=point,color=red,symbol=[
circle,cross]):\nplots[display]([p1,p2,p3],labels=[`x`,`y`]);" }}
{PARA 11 "" 1 "" {XPPMATH 20 "6#/-%\"fG6#%\"xG-%*PIECEWISEG6%7$F'2F'\"
\"!7$*$)F'\"\"#\"\"\"2F'F27$F1%*otherwiseG" }}{PARA 13 "" 1 ""
{GLPLOT2D 315 318 318 {PLOTDATA 2 "6)-%'CURVESG6&7U7$$!\"$\"\"!F(7$$!3
1;TY$Q6G\"H!#'**>F.FN7$$!3`80j^5*H\">F.FQ7$$!3zPdvJ\"3&H=F.FT7$$!3
%oy-Fk(p`9F.F]o7$$!3:>)***HRXL8F.F`o7$$!3wVI7&=/8D\"F.Fco
7$$!3A#G=Wa*el6F.Ffo7$$!3S^j.Zn(o3\"F.Fio7$$!3xr.LhV(>+\"F.F\\p7$$!3Si
liRk%y8*!#=F_p7$$!3QtZWdB:q$)FapFcp7$$!3!3!=-<<-TvFapFfp7$$!3'yKt\\j[W
o'FapFip7$$!3!=JIi)*ek%eFapF\\q7$$!3E6lW74mN]FapF_q7$$!3D*)oz))ySNTFap
Fbq7$$!3pNpn10\\ELFapFeq7$$!3+/eIT&)ziCFapFhq7$$!3?)383Dl,o\"FapF[r7$$
!3)H*=jPMSX#)!#>F^r7$$!38DL+_;-?UF`rFbr7$$!3wsvuj')RY>!#?Fer7$$\"3.yqk
gR/8SF`r$\"3d)f3I=_/h\"Fgr7$$\"3K8*owyF2A)F`r$\"3m#=&*e`O!enFgr7$$\"3;
)3meyG[k\"Fap$\"3')4P\"[thaq#F`r7$$\"3TI2Cw!yh]#Fap$\"3C)oH)\\&G4G'F`r
7$$\"3!4.jm\")fdL$Fap$\"3pxjWb$HF6\"Fap7$$\"3!yZ!Rlp7%=%Fap$\"3%Gx]i%=
p]H/tL)Fap7$$\"2%******R********F.$\"2!******z)*******F.7S7$$\"30+
++1+++5F.$\"\"#F*7$$\"3b]D?9VfV5F.F]w7$$\"3?!4s')[D:3\"F.F]w7$$\"3<%yg
91$=C6F.F]w7$$\"3;j>L'RBr;\"F.F]w7$$\"3%y3(GV'f)47F.F]w7$$\"3i))[$[h\"
[\\7F.F]w7$$\"3Mw%y8(y]!H\"F.F]w7$$\"3a@Xe%GPHL\"F.F]w7$$\"373V7E1Bv8F
.F]w7$$\"3;j/TEXt=9F.F]w7$$\"35v@Y&y_qX\"F.F]w7$$\"3!*H%*\\p+>+:F.F]w7
$$\"3w'[p$zW]V:F.F]w7$$\"3QiUCRfC&e\"F.F]w7$$\"3!*zQr$=^Ji\"F.F]w7$$\"
39%*>m&=C#o;F.F]w7$$\"33YuaIpS1
F.F]w7$$\"3+#)p/J;cc>F.F]w7$$\"3)\\HOQ#G,**>F.F]w7$$\"3k5SX#o2J/#F.F]w
7$$\"3gAb]'Q#\\\"3#F.F]w7$$\"3v'[k%=*[H7#F.F]w7$$\"3MnE]svxl@F.F]w7$$
\"33pp([0xw?#F.F]w7$$\"33\\`]ep@[AF.F]w7$$\"3I6.i4'HKH#F.F]w7$$\"3&*Rc
myanLBF.F]w7$$\"3!*>%po2goP#F.F]w7$$\"3Ve`LT<*fT#F.F]w7$$\"3;\"oBm)Hxe
CF.F]w7$$\"3C'e>W!o-*\\#F.F]w7$$\"3J*oEEk.6a#F.F]w7$$\"3GU*>HWTAe#F.F]
w7$$\"3>tSP2*3`i#F.F]w7$$\"3apHL%*zymEF.F]w7$$\"3L9dq^j?4FF.F]w7$$\"3?
YGmjMF^FF.F]w7$$\"3g8-jq(G**y#F.F]w7$$\"3SqRm9@BMGF.F]w7$$\"3)4w6PbdQ(
GF.F]w7$$\"3]!o,l`1h\"HF.F]w7$$\"3wn.)Q?Wl&HF.F]w7$$\"\"$F*F]w-%'COLOU
RG6&%$RGBG$\"*++++\"!\")$F*F*Ff`l-%*THICKNESSG6#F^w-%'POINTSG6$7$$\"\"
\"F*F]wF_`l-F$6&7#7$F^alF^alF_`l-%&STYLEG6#%&POINTG-%'SYMBOLG6#%'CIRCL
EG-F$6&7#F]alFhalF_`lFdal-F$6&F^bl-Fial6#%&CROSSGF_`lFdal-%+AXESLABELS
G6%Q\"x6\"Q!Fhbl-%%FONTG6#%(DEFAULTG-%%VIEWG6$;F(F]`lF]cl" 1 2 0 1 10
0 2 9 1 4 2 1.000000 45.000000 45.000000 0 0 "Curve 1" "Curve 2" "Curv
e 3" "Curve 4" "Curve 5" }}}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 "
;" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{PARA 0 "" 0 "" {TEXT -1 29 "It is intuitively clear that " }{XPPEDIT
18 0 "f(x);" "6#-%\"fG6#%\"xG" }{TEXT -1 21 " is discontinuous at " }
{XPPEDIT 18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 10 ", because " }
{XPPEDIT 18 0 "f(x);" "6#-%\"fG6#%\"xG" }{TEXT -1 46 " \"jumps\" from \+
values near 1 to the value 2 as " }{TEXT 307 1 "x" }{TEXT -1 22 " incr
eases through 1. " }}{PARA 0 "" 0 "" {TEXT -1 36 "There is a \"break\"
in the graph of " }{XPPEDIT 18 0 "y=f(x)" "6#/%\"yG-%\"fG6#%\"xG" }
{TEXT -1 7 " where " }{XPPEDIT 18 0 "x=1" "6#/%\"xG\"\"\"" }{TEXT -1
11 ". Indeed " }{XPPEDIT 18 0 "f(x)->1" "6#f*6#-%\"fG6#%\"xG7\"6$%)o
peratorG%&arrowG6\"\"\"\"F-F-F-" }{TEXT -1 5 ", as " }{XPPEDIT 18 0 "x
->1" "6#f*6#%\"xG7\"6$%)operatorG%&arrowG6\"\"\"\"F*F*F*" }{XPPEDIT
18 0 "``^`-`" "6#)%!G%\"-G" }{TEXT -1 8 ", while " }{XPPEDIT 18 0 "f(x
)->2" "6#f*6#-%\"fG6#%\"xG7\"6$%)operatorG%&arrowG6\"\"\"#F-F-F-" }
{TEXT -1 4 " as " }{XPPEDIT 18 0 "x->1" "6#f*6#%\"xG7\"6$%)operatorG%&
arrowG6\"\"\"\"F*F*F*" }{XPPEDIT 18 0 "``^`+` " "6#)%!G%\"+G" }{TEXT
-1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 80 "The function appears to be co
ntinuous at all other real number values including " }{XPPEDIT 18 0 "x
=0" "6#/%\"xG\"\"!" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }
}{PARA 0 "" 0 "" {TEXT -1 31 "We can check for continuity at " }
{XPPEDIT 18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 68 " with reference \+
to the 3 step analysis to see whether the condition " }{XPPEDIT 18 0 "
Limit(f(x),x = 1) = f(1);" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*\"\"\"-F(6#F
," }{TEXT -1 8 " holds. " }}{PARA 15 "" 0 "" {TEXT -1 7 " Since " }
{XPPEDIT 18 0 "f(x) = 2;" "6#/-%\"fG6#%\"xG\"\"#" }{TEXT -1 5 " for "
}{XPPEDIT 18 0 "2 <= x;" "6#1\"\"#%\"xG" }{TEXT -1 18 ", it follows th
at " }{XPPEDIT 18 0 "f(1) = 2;" "6#/-%\"fG6#\"\"\"\"\"#" }{TEXT -1 2 "
. " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "Limit(f(x),x = 1);" "6#-%&LimitG
6$-%\"fG6#%\"xG/F)\"\"\"" }{TEXT -1 25 " does not exist because " }
{XPPEDIT 18 0 "Limit(f(x),x = 1^`-`) = Limit(x^2,x = 1^`-`);" "6#/-%&L
imitG6$-%\"fG6#%\"xG/F*)\"\"\"%\"-G-F%6$*$F*\"\"#/F*)F-F." }{XPPEDIT
18 0 "`` = 1;" "6#/%!G\"\"\"" }{TEXT -1 9 ", while " }{XPPEDIT 18 0 "
Limit(f(x),x = 1^`+`) = Limit(2,x = 1^`+`);" "6#/-%&LimitG6$-%\"fG6#%
\"xG/F*)\"\"\"%\"+G-F%6$\"\"#/F*)F-F." }{XPPEDIT 18 0 "`` = 2;" "6#/%!
G\"\"#" }{TEXT -1 2 ". " }}{PARA 15 "" 0 "" {TEXT -1 40 "not applicabl
e because of the 2nd step. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA
0 "" 0 "" {TEXT -1 35 "Therefore, f is not continuous at " }{XPPEDIT
18 0 "x = 1;" "6#/%\"xG\"\"\"" }{TEXT -1 2 ". " }}{PARA 0 "" 0 ""
{TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 31 "We can check for continui
ty at " }{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }{TEXT -1 68 " with refer
ence to the 3 step analysis to see whether the condition " }{XPPEDIT
18 0 "Limit(f(x),x = 0) = f(0);" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*\"\"!-
F(6#F," }{TEXT -1 8 " holds. " }}{PARA 15 "" 0 "" {TEXT -1 7 " Since \+
" }{XPPEDIT 18 0 "f(x)=x^2" "6#/-%\"fG6#%\"xG*$F'\"\"#" }{TEXT -1 5 " \+
for " }{XPPEDIT 18 0 "0<=x" "6#1\"\"!%\"xG" }{XPPEDIT 18 0 "``<1" "6#2
%!G\"\"\"" }{TEXT -1 18 ", it follows that " }{XPPEDIT 18 0 "f(0)=0^2
" "6#/-%\"fG6#\"\"!*$F'\"\"#" }{XPPEDIT 18 0 "``=0" "6#/%!G\"\"!" }
{TEXT -1 3 ". " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "Limit(f(x),x = 0) =
0;" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*\"\"!F," }{TEXT -1 10 " because \+
" }{XPPEDIT 18 0 "Limit(f(x),x = 0^`-`) = Limit(x,x = 0^`-`);" "6#/-%&
LimitG6$-%\"fG6#%\"xG/F*)\"\"!%\"-G-F%6$F*/F*)F-F." }{XPPEDIT 18 0 " `
`=0" "6#/%!G\"\"!" }{TEXT -1 8 " while " }{XPPEDIT 18 0 "Limit(f(x),x
= 0^`+`) = Limit(x^2,x = 0^`+`);" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*)\"
\"!%\"+G-F%6$*$F*\"\"#/F*)F-F." }{XPPEDIT 18 0 "``=0" "6#/%!G\"\"!" }
{TEXT -1 7 " also. " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "Limit(f(x),x = \+
0)=0" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*\"\"!F," }{XPPEDIT 18 0 "``=f(0)
" "6#/%!G-%\"fG6#\"\"!" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0
"" }}{PARA 0 "" 0 "" {TEXT -1 14 "Therefore, f " }{TEXT 262 2 "is" }
{TEXT -1 15 " continuous at " }{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }
{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> "
0 "" {MPLTEXT 1 0 1 ";" }}}}{SECT 1 {PARA 4 "" 0 "" {TEXT -1 10 "Examp
le 4 " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 79 "
Consider the function f defined for all real numbers by the piecewise \+
formula: " }}{PARA 257 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "f(x) = P
IECEWISE([(x^3+1)/(x+1), x <> -1], [2, x = -1])" "6#/-%\"fG6#%\"xG-%*P
IECEWISEG6$7$*&,&*$F'\"\"$\"\"\"F0F0F0,&F'F0F0F0!\"\"0F',$F0F27$\"\"#/
F',$F0F2" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 14 "The graph of
" }{XPPEDIT 18 0 "y=f(x)" "6#/%\"yG-%\"fG6#%\"xG" }{TEXT -1 26 " can
be drawn as follows. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG
{PARA 0 "> " 0 "" {MPLTEXT 1 0 303 "f := x -> piecewise(x<>-1,(x^3+1)/
(x+1),x=-1,2):\n'f(x)'=f(x);\np1 := plot(f(x),x=-2.2..3.2,0..8,thickne
ss=1):\np2 := plot([[-1,3]],style=point,color=red,symbol=circle,symbol
size=10):\np3 := plot([[[-1,2]]$3],style=point,color=red,symbol=[circl
e,diamond,cross]):\nplots[display]([p1,p2,p3],labels=[`x`,`y`]);" }}
{PARA 11 "" 1 "" {XPPMATH 20 "6#/-%\"fG6#%\"xG-%*PIECEWISEG6$7$*&,&*$)
F'\"\"$\"\"\"F1F1F1F1,&F1F1F'F1!\"\"0F'F37$\"\"#/F'F3" }}{PARA 13 ""
1 "" {GLPLOT2D 404 412 412 {PLOTDATA 2 "6)-%'CURVESG6%7S7$$!3;+++++++A
!#<$\"3#4++++++/)F*7$$!3+++]n`H#3#F*$\"3kf>,l$\\#=uF*7$$!3C+]7'>\"))z>
F*$\"3!>O%*ou5)**oF*7$$!35++D\\dqk=F*$\"3[/g`!GL=M'F*7$$!3+++vWow[WF*7$$!3<+]7X$p5I\"F*$\"3c
(**[fy]Q*RF*7$$!3A+]iAt(o=\"F*$\"3/*['e,^b&f$F*7$$!39++]\"z;%p5F*$\"3?
b@Wl!pI@$F*7$$!3I-+]<\\df'*!#=$\"3?]zhn8.**GF*7$$!39+++X#o[\\)F\\o$\"3
]$4*\\*o96d#F*7$$!3\">++]'F
\\o$\"3#o.C?hKS+#F*7$$!3)3+]7:=\\<&F\\o$\"3Knj%Qf*G&y\"F*7$$!3k+++&4Zz
&RF\\o$\"3a*=o:;[Cb\"F*7$$!35,++!)H,FHF\\o$\"3)[)3&yMv$y8F*7$$!3Y***\\
7_\"zF$\"3m>Z!y)p1r5F*7$$\"3A2+
](y>P)\\Feq$\"3!yJqT[lk_*F\\o7$$\"39***\\i`$R2;F\\o$\"3eGyyhy(4l)F\\o7
$$\"3a-+](=TXw#F\\o$\"3i*QQ-hF(**zF\\o7$$\"3H,+v`R;FQF\\o$\"3?L$Q\"RWb
PwF\\o7$$\"3i)***\\ihMt\\F\\o$\"3TZ`qU52+vF\\o7$$\"3e***\\([t!R;'F\\o$
\"3\\DukJ!oaj(F\\o7$$\"3A***\\7O%H+sF\\o$\"3#Q&[hF&HT)zF\\o7$$\"3:,+]F
2i>$)F\\o$\"3ujZWx\"))>g)F\\o7$$\"3m(******Q%*fZ*F\\o$\"3\"F*7$$\"3q***\\-%*>F*$\"3SBXon?Y%)GF*7$$\"3K***
*\\#*=0s?F*$\"3BHGr_rM@KF*7$$\"35+](o/M$)=#F*$\"3F:t$Q&=Z+OF*7$$\"3V++
+#eF.I#F*$\"3Go*4DSz6*RF*7$$\"3A++DZr&[T#F*$\"3;4WP%*yn;WF*7$$\"3\\+](
)\\$Q%GDF*$\"39:OCR@ck[F*7$$\"3!*******yw!Gj#F*$\"3-n8g&fo))H&F*7$$\"3
!)***\\#3nU_FF*$\"3W69ooF*7$$\"3?+]7]$pE3$F*$\"3'34v?(4=?uF*7$$\"3;++
+++++KF*F+-%'COLOURG6&%$RGBG$\"#5!\"\"$\"\"!F_[lF^[l-%*THICKNESSG6#\"
\"\"-F$6&7#7$$F][lF_[l$\"\"$F_[l-Fhz6&Fjz$\"*++++\"!\")F^[lF^[l-%'SYMB
OLG6$%'CIRCLEGF\\[l-%&STYLEG6#%&POINTG-F$6&7#7$Fh[l$\"\"#F_[l-Fa\\l6#F
c\\lF[\\lFd\\l-F$6&Fj\\l-Fa\\l6#%(DIAMONDGF[\\lFd\\l-F$6&Fj\\l-Fa\\l6#
%&CROSSGF[\\lFd\\l-%+AXESLABELSG6%%\"xG%\"yG-%%FONTG6#%(DEFAULTG-%%VIE
WG6$;$!#AF][l$\"#KF][l;F^[l$\"\")F_[l" 1 2 0 1 10 0 2 9 1 4 2
1.000000 45.000000 45.000000 0 0 "Curve 1" "Curve 2" "Curve 3" "Curve \+
4" "Curve 5" }}}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}{PARA
0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 ""
0 "" {TEXT -1 29 "It is intuitively clear that " }{XPPEDIT 18 0 "f(x);
" "6#-%\"fG6#%\"xG" }{TEXT -1 21 " is discontinuous at " }{XPPEDIT 18
0 "x = -1;" "6#/%\"xG,$\"\"\"!\"\"" }{TEXT -1 14 ", because, as " }
{TEXT 309 1 "x" }{TEXT -1 19 " increases through " }{XPPEDIT 18 0 "-1
" "6#,$\"\"\"!\"\"" }{TEXT -1 2 ", " }{XPPEDIT 18 0 "f(x);" "6#-%\"fG6
#%\"xG" }{TEXT -1 46 " \"jumps\" from values near 3 to the value 2 at \+
" }{XPPEDIT 18 0 "x = -1;" "6#/%\"xG,$\"\"\"!\"\"" }{TEXT -1 42 ", and
then \"jumps\" back to values near 3. " }}{PARA 0 "" 0 "" {TEXT -1
36 "There is a \"break\" in the graph of " }{XPPEDIT 18 0 "y=f(x)" "6
#/%\"yG-%\"fG6#%\"xG" }{TEXT -1 7 " where " }{XPPEDIT 18 0 "x = -1;" "
6#/%\"xG,$\"\"\"!\"\"" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 68
"The function appears to be continuous at all non-zero real numbers. \+
" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 31 "We ca
n check for continuity at " }{XPPEDIT 18 0 "x = -1;" "6#/%\"xG,$\"\"\"
!\"\"" }{TEXT -1 68 " with reference to the 3 step analysis to see whe
ther the condition " }{XPPEDIT 18 0 "Limit(f(x),x = -1) = f(-1);" "6#/
-%&LimitG6$-%\"fG6#%\"xG/F*,$\"\"\"!\"\"-F(6#,$F-F." }{TEXT -1 8 " hol
ds. " }}{PARA 15 "" 0 "" {TEXT -1 50 " The piecewise formula for f giv
es the value 2 at " }{XPPEDIT 18 0 "x = -1;" "6#/%\"xG,$\"\"\"!\"\"" }
{TEXT -1 11 ", that is, " }{XPPEDIT 18 0 "f(-1) = 2;" "6#/-%\"fG6#,$\"
\"\"!\"\"\"\"#" }{TEXT -1 2 ". " }}{PARA 258 "" 0 "" {TEXT -1 1 " " }
{XPPEDIT 18 0 "Limit(f(x),x=-1)=Limit((x^3+1)/(x+1),x=-1)" "6#/-%&Limi
tG6$-%\"fG6#%\"xG/F*,$\"\"\"!\"\"-F%6$*&,&*$F*\"\"$F-F-F-F-,&F*F-F-F-F
./F*,$F-F." }{TEXT -1 3 " \n " }{XPPEDIT 18 0 "``=Limit((x+1)*(x^2-x+1
)/(x+1),x=-1)" "6#/%!G-%&LimitG6$*(,&%\"xG\"\"\"F+F+F+,(*$F*\"\"#F+F*!
\"\"F+F+F+,&F*F+F+F+F//F*,$F+F/" }{TEXT -1 3 " \n " }{XPPEDIT 18 0 "``
=Limit(x^2-x+1,x=-1)" "6#/%!G-%&LimitG6$,(*$%\"xG\"\"#\"\"\"F*!\"\"F,F
,/F*,$F,F-" }{TEXT -1 3 " \n " }{XPPEDIT 18 0 "``=3" "6#/%!G\"\"$" }
{TEXT -1 2 ". " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "Limit(f(x),x = -1) <
> f(-1);" "6#0-%&LimitG6$-%\"fG6#%\"xG/F*,$\"\"\"!\"\"-F(6#,$F-F." }
{TEXT -1 10 " because " }{XPPEDIT 18 0 "Limit(f(x),x = -1) = 3;" "6#/
-%&LimitG6$-%\"fG6#%\"xG/F*,$\"\"\"!\"\"\"\"$" }{TEXT -1 8 " while "
}{XPPEDIT 18 0 "f(-1) = 2;" "6#/-%\"fG6#,$\"\"\"!\"\"\"\"#" }{TEXT -1
2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 35 "
Therefore, f is not continuous at " }{XPPEDIT 18 0 "x = -1;" "6#/%\"x
G,$\"\"\"!\"\"" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{PARA 0 "" 0 "" {TEXT 261 4 "Note" }{TEXT -1 63 ": The function f can \+
also be defined by the (simpler) formula: " }}{PARA 257 "" 0 "" {TEXT
-1 1 " " }{XPPEDIT 18 0 "f(x) = PIECEWISE([x^2-x+1, x <> -1],[2, x = -
1]);" "6#/-%\"fG6#%\"xG-%*PIECEWISEG6$7$,(*$F'\"\"#\"\"\"F'!\"\"F/F/0F
',$F/F07$F./F',$F/F0" }{TEXT -1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "
" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}}{SECT 1 {PARA 4 "
" 0 "" {TEXT -1 10 "Example 5 " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{PARA 0 "" 0 "" {TEXT -1 79 "Consider the function f defined for all r
eal numbers by the piecewise formula: " }}{PARA 257 "" 0 "" {TEXT -1
1 " " }{XPPEDIT 18 0 "f(x) = PIECEWISE([2-sqrt(-x), x < 0],[1, x = 0],
[2-sqrt(x), 0 < x]);" "6#/-%\"fG6#%\"xG-%*PIECEWISEG6%7$,&\"\"#\"\"\"-
%%sqrtG6#,$F'!\"\"F32F'\"\"!7$F./F'F57$,&F-F.-F06#F'F32F5F'" }{TEXT
-1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 14 "The graph of " }{XPPEDIT 18
0 "y=f(x)" "6#/%\"yG-%\"fG6#%\"xG" }{TEXT -1 16 " is as follows. " }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0
300 "f := x -> piecewise(x<0,2-sqrt(-x),x=0,1,x>0,2-sqrt(x)):\n'f(x)'=
f(x);\np1 := plot(f(x),x=-6..6,thickness=2):\np2 := plot([[0,2]],style
=point,color=red,symbol=circle,symbolsize=10):\np3 := plot([[[0,1]]$3]
,style=point,color=red,symbol=[circle,diamond,cross]):\nplots[display]
([p1,p2,p3],labels=[`x`,`y`]);" }}{PARA 11 "" 1 "" {XPPMATH 20 "6#/-%
\"fG6#%\"xG-%*PIECEWISEG6%7$,&\"\"#\"\"\"*$,$F'!\"\"#F.F-F12F'\"\"!7$F
./F'F47$,&F-F.*$F'F2F12F4F'" }}{PARA 13 "" 1 "" {GLPLOT2D 625 178 178
{PLOTDATA 2 "6)-%'CURVESG6%7en7$$!\"'\"\"!$!3!)y<$yU(*[\\%!#=7$$!3z***
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l;!\\D&F1$!3yR(R#*GsN#HF-7$$!3o*****\\lfs*\\F1$!3k`$zuL^XN#F-7$$!3%)**
**\\s@%3u%F1$!3g?tP%3vMx\"F-7$$!3J++]U.6.XF1$!3q'p8oJL0A\"F-7$$!3')***
*\\-G&pD%F1$!3\")HOW*fUQK'!#>7$$!3(*****\\AjP-SF1$!3=_'=D=C*Rf!#@7$$!3
3++]sih[PF1$\"35pW[wOc'Q'FR7$$!3%)******pGf([$F1$\"3Oz>ua>!\\K\"F-7$$!
3)******\\J$odKF1$\"3'o3i1_Y4&>F-7$$!3y******4'f))*HF1$\"3KDsefUy#o#F-
7$$!33+++]J(*QFF1$\"3w>qEZm:]MF-7$$!3#)*******QC&)[#F1$\"3KWn1/D%\\A%F
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F-7$$!3'*******R%e:w\"F1$\"3B4!)[Y&Gws'F-7$$!33++]#yk]\\\"F1$\"3GS%*)o
#ersxF-7$$!3M+++SF)***F-7$$!3(p****\\ZD\"RvF-$\"3>3_BC'=<8\"F17$$!3I'*****\\ion\\F-$
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-jg#F-$\"3O?m()G/[*[\"F17$$!3Q(**\\7VM&p>F-$\"3'32$oHc?c:F17$$!3j)***
\\PlwK8F-$\"3q@cH[#H\\j\"F17$$!3o)***\\Pk)*fpFR$\"3#[Gxy8#=OF17$$\"3I*)**\\78#>-'FR$\"3]R+xmRgaF-$\"3m^!eAYZ7c\"F17$$
\"3/*****\\xgke#F-$\"3uy*oam%**F-$\"3Fdytc3n-5F17$$\"3k*****\\JigC\"F1
$\"35>VZlQGP))F-7$$\"3%*****\\PIFU,UF-7$$\"
3q+++5zj_FF1$\"3718vcV#*3MF-7$$\"3=****\\<3;%*HF1$\"3k`)zCScjp#F-7$$\"
3;++]Z=iYKF1$\"3w`#3zO:;)>F-7$$\"3[******\\'[M\\$F1$\"3&3S\"o'[I#48F-7
$$\"3W****\\PM&=v$F1$\"3(4A[30$)HI'FR7$$\"3v+++gzs+SF1$!3fbTj1s\")>=FX
7$$\"35+++0\"Q_D%F1$!3ad37n[G#G'FR7$$\"3q++]x2k2XF1$!3y2_b#G07B\"F-7$$
\"3d+++?EdRZF1$!3Uz\\FC&f0x\"F-7$$\"3M+++&o#R0]F1$!3a84jN\\tsBF-7$$\"3
++++?`9V_F1$!3-1](4X:z*GF-7$$\"3G++]<#Rm\\&F1$!33Z#R=\\7\\W$F-7$$\"3F+
+]A_ERdF1$!3a$zH8gjn&RF-7$$\"\"'F*F+-%'COLOURG6&%$RGBG$\"#5!\"\"$F*F*F
i]l-%*THICKNESSG6#\"\"#-F$6&7#7$Fi]l$F]^lF*-Fc]l6&Fe]l$\"*++++\"!\")Fi
]lFi]l-%&STYLEG6#%&POINTG-%'SYMBOLG6$%'CIRCLEGFg]l-F$6&7#7$Fi]l$\"\"\"
F*-F]_l6#F__lFc^lFh^l-F$6&Fb_l-F]_l6#%(DIAMONDGFc^lFh^l-F$6&Fb_l-F]_l6
#%&CROSSGFc^lFh^l-%+AXESLABELSG6%%\"xG%\"yG-%%FONTG6#%(DEFAULTG-%%VIEW
G6$;F(F`]lFj`l" 1 2 0 1 10 0 2 9 1 4 2 1.000000 45.000000 45.000000 0
0 "Curve 1" "Curve 2" "Curve 3" "Curve 4" "Curve 5" }}}}{EXCHG {PARA
0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 29 "It is int
uitively clear that " }{XPPEDIT 18 0 "f(x);" "6#-%\"fG6#%\"xG" }{TEXT
-1 21 " is discontinuous at " }{XPPEDIT 18 0 "x = 0;" "6#/%\"xG\"\"!"
}{TEXT -1 14 ", because, as " }{TEXT 308 1 "x" }{TEXT -1 22 " increase
s through 0, " }{XPPEDIT 18 0 "f(x);" "6#-%\"fG6#%\"xG" }{TEXT -1 46 "
\"jumps\" from values near 2 to the value 1 at " }{XPPEDIT 18 0 "x=0
" "6#/%\"xG\"\"!" }{TEXT -1 42 ", and then \"jumps\" back to values ne
ar 2. " }}{PARA 0 "" 0 "" {TEXT -1 36 "There is a \"break\" in the gra
ph of " }{XPPEDIT 18 0 "y=f(x)" "6#/%\"yG-%\"fG6#%\"xG" }{TEXT -1 7 "
where " }{XPPEDIT 18 0 "x = 0;" "6#/%\"xG\"\"!" }{TEXT -1 2 ". " }}
{PARA 0 "" 0 "" {TEXT -1 68 "The function appears to be continuous at \+
all non-zero real numbers. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA
0 "" 0 "" {TEXT -1 31 "We can check for continuity at " }{XPPEDIT 18
0 "x = 0;" "6#/%\"xG\"\"!" }{TEXT -1 68 " with reference to the 3 step
analysis to see whether the condition " }{XPPEDIT 18 0 "Limit(f(x),x \+
= 0) = f(0);" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*\"\"!-F(6#F," }{TEXT -1
8 " holds. " }}{PARA 15 "" 0 "" {TEXT -1 50 " The piecewise formula fo
r f gives the value 1 at " }{XPPEDIT 18 0 "x=0" "6#/%\"xG\"\"!" }
{TEXT -1 11 ", that is, " }{XPPEDIT 18 0 "f(0) = 1;" "6#/-%\"fG6#\"\"!
\"\"\"" }{TEXT -1 2 ". " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "Limit(f(x),
x = 0) = 2;" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*\"\"!\"\"#" }{TEXT -1 11 "
because " }{XPPEDIT 18 0 "Limit(f(x),x = 0^`-`) = Limit(2-sqrt(-x),
x = 0^`-`);" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*)\"\"!%\"-G-F%6$,&\"\"#\"
\"\"-%%sqrtG6#,$F*!\"\"F8/F*)F-F." }{XPPEDIT 18 0 "`` = 2;" "6#/%!G\"
\"#" }{TEXT -1 9 ", while " }{XPPEDIT 18 0 "Limit(f(x),x = 0^`+`) = L
imit(2-sqrt(x),x = 0^`+`);" "6#/-%&LimitG6$-%\"fG6#%\"xG/F*)\"\"!%\"+G
-F%6$,&\"\"#\"\"\"-%%sqrtG6#F*!\"\"/F*)F-F." }{XPPEDIT 18 0 "`` = 2;"
"6#/%!G\"\"#" }{TEXT -1 2 ". " }}{PARA 15 "" 0 "" {XPPEDIT 18 0 "Limit
(f(x),x = 0) <> f(0)" "6#0-%&LimitG6$-%\"fG6#%\"xG/F*\"\"!-F(6#F," }
{TEXT -1 10 " because " }{XPPEDIT 18 0 "Limit(f(x),x = 0) = 2" "6#/-%
&LimitG6$-%\"fG6#%\"xG/F*\"\"!\"\"#" }{TEXT -1 8 " while " }{XPPEDIT
18 0 "f(0)=1" "6#/-%\"fG6#\"\"!\"\"\"" }{TEXT -1 2 ". " }}{PARA 0 ""
0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 35 "Therefore, f is not
continuous at " }{XPPEDIT 18 0 "x = 0;" "6#/%\"xG\"\"!" }{TEXT -1 2 "
. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 261 4 "Not
e" }{TEXT -1 53 ": The function f can also be defined by the formula: \+
" }}{PARA 260 "" 0 "" {TEXT -1 1 " " }{XPPEDIT 18 0 "f(x) = PIECEWISE(
[2-sqrt(abs(x)), x <> 0],[1, x = 0]);" "6#/-%\"fG6#%\"xG-%*PIECEWISEG6
$7$,&\"\"#\"\"\"-%%sqrtG6#-%$absG6#F'!\"\"0F'\"\"!7$F./F'F7" }{TEXT
-1 2 ". " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 ""
{MPLTEXT 1 0 1 ";" }}}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}
}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}
{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 1 ";" }}}{SECT 1 {PARA 0 "" 0 "
" {TEXT -1 17 "Code for picture " }}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT
1 0 1 ";" }}}{SECT 1 {PARA 0 "" 0 "" {TEXT -1 29 "Graph of continuous \+
function " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}{EXCHG {PARA 0 "> " 0 ""
{MPLTEXT 1 0 458 "f := x ->2+(x+2)^3/3: \np1 := plot(f(x),x=0.5..1.5,t
hickness=2,color=red):\np2 := plot([[0,0],[2,0]],color=black):\np3 := \+
plot([[1,0],[1,f(1)]],color=black,linestyle=2):\np4 := plot([[[1,f(1)]
]$3],style=point,symbol=[circle,diamond,cross],color=red):\nt1 := plot
s[textplot]([[1,-.6,`x = a`],[0.85,12,`( a,f(a) )`]],color=COLOR(RGB,.
01,0,0)):\nt2 := plots[textplot]([[1.45,13,`y = f(x)`]],color=red):\np
lots[display]([p||(1..4),t1,t2],view=[0..2,-.6..17],axes=none);" }}
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