{VERSION 5 0 "IBM INTEL NT" "5.0" } {USTYLETAB {CSTYLE "Maple Input" -1 0 "Courier" 0 1 255 0 0 1 0 1 0 0 1 0 0 0 0 1 }{CSTYLE "2D Math" -1 2 "Times" 0 1 110 32 42 0 0 0 2 0 0 0 0 0 0 1 }{CSTYLE "2D Comment" 2 18 "" 0 1 0 0 42 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "Define" -1 256 "Times" 1 12 163 163 163 0 1 1 0 0 0 0 0 0 0 1 }{CSTYLE "Emphasis" -1 257 "Times" 1 12 128 0 128 1 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "normal C" -1 258 "Times" 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "Menu" -1 259 "" 0 0 163 163 163 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 260 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 261 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 262 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 263 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 264 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 265 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 266 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 267 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 268 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 269 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 270 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 271 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 272 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 273 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 274 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 275 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 276 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 277 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 278 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 279 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 280 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{PSTYLE "Normal " -1 0 1 {CSTYLE "" -1 -1 "Geneva" 1 10 0 0 0 1 2 2 2 2 2 2 1 1 1 1 } 1 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "R3 Font 0" -1 256 1 {CSTYLE "" -1 -1 "Monaco" 1 9 255 0 0 1 2 2 2 2 2 2 1 1 1 1 }1 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "R3 Font 0" -1 257 1 {CSTYLE "" -1 -1 "Geneva" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }1 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "R3 \+ Font 2" -1 258 1 {CSTYLE "" -1 -1 "Geneva" 1 10 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }1 1 0 0 0 0 1 0 1 0 2 2 0 1 }} {SECT 0 {EXCHG {PARA 257 "" 0 "" {TEXT 257 41 "COMPLEX ANALYSIS: Maple Worksheets, 2001" }{TEXT 275 144 "\n(c) John H. Mathews Rus sell W. Howell\nmathews@fullerton.edu howell@westmont.edu\n\nCompl imentary software to accompany the textbook:" }}{PARA 257 "" 0 "" {TEXT 257 82 "COMPLEX ANALYSIS: for Mathematics & Engineering, 4th Ed, 2001, ISBN: 0-7637-1425-9" }{TEXT 274 197 "\nJones and Bartlett Publi shers, Inc., 40 Tall Pine Drive, Sudbury, MA 01776\nTel e. (800) 832-0034; FAX: (508) 443-8000, E-mail: mkt@jbpu b.com, http://www.jbpub.com/" }}}{EXCHG {PARA 257 "" 0 "" {TEXT 272 1 "\n" }{TEXT 256 36 "CHAPTER 7 TAYLOR and LAURENT SERIES" } {TEXT 269 2 "\n\n" }{TEXT 256 55 "Section 7.5 Applications of Taylor \+ and Laurent Series\n" }{TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 250 " \+ In this section we show how Taylor and Laurent series can be used to derive important properties of analytic functions. We begin by showin g that the zeros of an analytic function must be \"isolated\" unless t he function is identically zero. A point " }{XPPEDIT 18 0 "alpha" "6#% &alphaG" }{TEXT -1 11 " of a set " }{XPPEDIT 18 0 "T;" "6#%\"TG" } {TEXT -1 12 " is called " }{TEXT 276 8 "isolated" }{TEXT -1 24 " if t here exists a disk " }{XPPEDIT 18 0 "D[r](alpha)" "6#-&%\"DG6#%\"rG6#% &alphaG" }{TEXT -1 7 " about " }{XPPEDIT 18 0 "alpha" "6#%&alphaG" } {TEXT -1 44 " that does not contain any other points of " }{XPPEDIT 18 0 "T" "6#%\"TG" }{TEXT -1 3 ". " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 256 12 "Theorem 7.13" }{TEXT -1 12 " Suppose " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 18 " is analytic at " } {XPPEDIT 18 0 "z=alpha" "6#/%\"zG%&alphaG" }{TEXT -1 12 " and that \+ " }{XPPEDIT 18 0 "f(alpha)=0" "6#/-%\"fG6#%&alphaG\"\"!" }{TEXT -1 8 " . If " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 64 " is \+ \nnot identically zero, then there exists a punctured disk " } {XPPEDIT 18 0 "D[r](alpha)^`*`" "6#)-&%\"DG6#%\"rG6#%&alphaG%\"*G" } {TEXT -1 12 " in which " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" } {TEXT -1 17 " has no zeros. " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 " " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 256 34 "Corollary 7.11 (L'Hopital's rule)" }{TEXT -1 12 " Suppose " } {XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 7 " and " } {XPPEDIT 18 0 "g(z)" "6#-%\"gG6#%\"zG" }{TEXT -1 19 " are analytic at " }{XPPEDIT 18 0 "z = alpha" "6#/%\"zG%&alphaG" }{TEXT -1 4 " . " } }{PARA 0 "" 0 "" {TEXT -1 5 "\nIf " }{XPPEDIT 18 0 "f(alpha) = 0" "6# /-%\"fG6#%&alphaG\"\"!" }{TEXT -1 7 " and " }{XPPEDIT 18 0 "g(alpha) = 0" "6#/-%\"gG6#%&alphaG\"\"!" }{TEXT -1 7 " but " }{XPPEDIT 18 0 "`g '`(alpha) <> 0" "6#0-%$g~'G6#%&alphaG\"\"!" }{TEXT -1 11 " , then " }{XPPEDIT 18 0 "limit(f(z)/g(z),z=alpha)" "6#-%&limitG6$*&-%\"fG6 #%\"zG\"\"\"-%\"gG6#F*!\"\"/F*%&alphaG" }{TEXT -1 3 " = " }{XPPEDIT 18 0 "limit(`f '`(z)/`g '`(z),z=alpha) = `f '`(alpha)/`g '`(alpha)" "6 #/-%&limitG6$*&-%$f~'G6#%\"zG\"\"\"-%$g~'G6#F+!\"\"/F+%&alphaG*&-F)6#F 2F,-F.6#F2F0" }{TEXT -1 3 " . " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 " " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 256 40 "Theorem 7.14 (Division of power series)" }{TEXT -1 11 " \nSuppose " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 7 " and " } {XPPEDIT 18 0 "g(z)" "6#-%\"gG6#%\"zG" }{TEXT -1 19 " are analytic at " }{XPPEDIT 18 0 "z=alpha" "6#/%\"zG%&alphaG" }{TEXT -1 36 " with p ower series representations\n" }{XPPEDIT 18 0 "f(z) = sum(a[n]*(z-alph a)^n,n=0..infinity)" "6#/-%\"fG6#%\"zG-%$sumG6$*&&%\"aG6#%\"nG\"\"\"), &F'F0%&alphaG!\"\"F/F0/F/;\"\"!%)infinityG" }{TEXT 277 9 " for " } {XPPEDIT 18 0 "`z`*epsilon*D[R](alpha)" "6#*(%\"zG\"\"\"%(epsilonGF%-& %\"DG6#%\"RG6#%&alphaGF%" }{TEXT 279 9 " and " }{XPPEDIT 18 0 "g(z ) = sum(b[n]*(z-alpha)^n,n=0..infinity)" "6#/-%\"gG6#%\"zG-%$sumG6$*&& %\"bG6#%\"nG\"\"\"),&F'F0%&alphaG!\"\"F/F0/F/;\"\"!%)infinityG" } {TEXT 278 9 " for " }{XPPEDIT 18 0 "`z`*epsilon*D[R](alpha)" "6#*( %\"zG\"\"\"%(epsilonGF%-&%\"DG6#%\"RG6#%&alphaGF%" }{TEXT 280 2 " ." } {TEXT -1 5 "\nIf " }{XPPEDIT 18 0 "g(alpha) <> 0" "6#0-%\"gG6#%&alpha G\"\"!" }{TEXT -1 23 " , then the quotient " }{XPPEDIT 18 0 "f(z)/g( z)" "6#*&-%\"fG6#%\"zG\"\"\"-%\"gG6#F'!\"\"" }{TEXT -1 39 " has the \+ power series representation\n" }{XPPEDIT 18 0 "f(z)/g(z) = sum(c[n]*(z -alpha)^n,n=0..infinity)" "6#/*&-%\"fG6#%\"zG\"\"\"-%\"gG6#F(!\"\"-%$s umG6$*&&%\"cG6#%\"nGF)),&F(F)%&alphaGF-F5F)/F5;\"\"!%)infinityG" } {TEXT -1 51 " , where the coefficients satisfy the equations \n" } {XPPEDIT 18 0 "a[n] = b[0]*c[n] + b[1]*c[n-1] + `...`+b[n-1]*c[1] + b[ n]*c[0]" "6#/&%\"aG6#%\"nG,,*&&%\"bG6#\"\"!\"\"\"&%\"cG6#F'F.F.*&&F+6# F.F.&F06#,&F'F.F.!\"\"F.F.%$...GF.*&&F+6#,&F'F.F.F8F.&F06#F.F.F.*&&F+6 #F'F.&F06#F-F.F." }{TEXT -1 49 " . \nIn other words, the series for th e quotient " }{XPPEDIT 18 0 "f(z)/g(z)" "6#*&-%\"fG6#%\"zG\"\"\"-%\"g G6#F'!\"\"" }{TEXT -1 71 " can be obtained by the familiar process of \ndividing the series for " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 21 " by the series for " }{XPPEDIT 18 0 "g(z)" "6#-%\"gG6# %\"zG" }{TEXT -1 46 " using the standard long division algorithm. " } }}{EXCHG {PARA 257 "" 0 "" {TEXT 273 1 "\n" }{TEXT 256 23 "Example 7.1 5, Page 300." }{TEXT 270 56 " Find the firt few terms of the \nMaclau rin series for " }{XPPEDIT 18 0 "f(z) = sec(z)" "6#/-%\"fG6#%\"zG-%$s ecG6#F'" }{TEXT 266 27 " and use it to compute " }{XPPEDIT 18 0 "f ^` (4)`*`(0)`" "6#*&)%\"fG%%~(4)G\"\"\"%$(0)GF'" }{TEXT 260 3 " .\n" } }{PARA 0 "> " 0 "" {MPLTEXT 1 0 190 "f:='f': p:='p': P:='P': S:='S': z :='z': Z:='Z':\nf := z -> sec(z):\nS := series(f(Z), Z=0, 14):\np := z -> subs(Z=z,convert(S, polynom)):\n`f(z) ` = f(z);\n`f(z) ` = subs(Z= z,S);\nP[12](z) = p(z);" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 44 "Or we \+ could use Maple's \"unapply\" procedure." }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 201 "f:='f': p:='p': P:='P': s:='s': t:='t': z:='z': Z:=' Z':\nf := z -> sec(z):\nS := taylor(f(z), z=0, 14):\np:=unapply(conver t(taylor(f(z),z=0,14),polynom),z):\n`f(z) ` = f(z);\n`f(z) ` = S;\nP [12](z) = p(z);" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 457 "D4 := s implify(diff(f(Z), Z$4)):\nf4 := z -> subs(Z=z, D4):\nS4 := simplify(d iff(p(Z), Z$4)):\np4 := z -> subs(Z=z, S4):\n`f'(z) ` = simplify(diff( f(z), z));\n`p'(z) ` = simplify(diff(p(z), z)); ` `;\n`f''(z) ` = simp lify(diff(f(z), z$2));\n`p''(z) ` = simplify(diff(p(z), z$2)); ` `;\n` f'''(z) ` = simplify(diff(f(z), z$3));\n`p'''(z) ` = simplify(diff(p(z ), z$3)); ` `;\n`f''''(z) ` = f4(z);\n`p''''(z) ` = p4(z); ` `;\n`f''' '(0) ` = eval(f4(0));\n`p''''(0) ` = p4(0);" }}}{EXCHG {PARA 0 "" 0 " " {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 256 23 "Theorem 7.15 (Riemann)" }{TEXT -1 17 " Suppose t hat " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 18 " is anal ytic in " }{XPPEDIT 18 0 "D[r](alpha)^`*`" "6#)-&%\"DG6#%\"rG6#%&alph aG%\"*G" }{TEXT -1 8 " . \nIf " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"z G" }{TEXT -1 17 " is bounded in " }{XPPEDIT 18 0 "D[r](alpha)^`*`" " 6#)-&%\"DG6#%\"rG6#%&alphaG%\"*G" }{TEXT -1 17 " , then either " } {XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 18 " is analytic at \+ " }{XPPEDIT 18 0 "z = alpha" "6#/%\"zG%&alphaG" }{TEXT -1 6 " or " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 35 " has a removabl e \nsingularity at " }{XPPEDIT 18 0 "z = alpha" "6#/%\"zG%&alphaG" } {TEXT -1 3 " . " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 256 12 "Theorem 7.16" }{TEXT -1 17 " The function " } {XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 30 " has a pole of o rder k at " }{XPPEDIT 18 0 "z = alpha" "6#/%\"zG%&alphaG" }{TEXT -1 20 " \nif and only if " }{XPPEDIT 18 0 "limit(abs(f(z)), z=alpha ) = infinity" "6#/-%&limitG6$-%$absG6#-%\"fG6#%\"zG/F-%&alphaG%)infini tyG" }{TEXT -1 3 " . " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }} {PARA 0 "" 0 "" {TEXT 256 12 "Theorem 7.18" }{TEXT -1 17 " The funct ion " }{XPPEDIT 18 0 "f(z)" "6#-%\"fG6#%\"zG" }{TEXT -1 34 " has an \+ essential singularity at " }{XPPEDIT 18 0 "z = alpha" "6#/%\"zG%&alpha G" }{TEXT -1 19 " \nif and only if " }{XPPEDIT 18 0 "limit(abs(f(z)) , z=alpha) " "6#-%&limitG6$-%$absG6#-%\"fG6#%\"zG/F,%&alphaG" }{TEXT -1 18 " does not exist. " }}}{EXCHG {PARA 257 "" 0 "" {TEXT 256 23 "E xample 7.16, Page 302." }{TEXT 271 26 " Show that the function " } {XPPEDIT 18 0 "g(z) = exp(-1/z^2)" "6#/-%\"gG6#%\"zG-%$expG6#,$*&\"\" \"F-*$F'\"\"#!\"\"F0" }{TEXT 261 25 " \nis NOT continuous at " } {XPPEDIT 18 0 "z = 0" "6#/%\"zG\"\"!" }{TEXT 267 3 " .\n" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 347 "g:='g': G:='G': x:='x': y:='y': z:='z':\nG : = z -> exp(-1/z^2):\n`g(z) ` = G(z); ` `;\n`g(x + I*0) ` = evalc(G(x + I*0)),` and `,\n`g(0 + I*y) ` = evalc(G(0 + I*y));\nLimit(g(x), x =0, right),` = `,\nLimit(G(x), x=0, right) = limit(G(x), x=0, righ t);\nLimit(g(0 + I*y), y=0, right),` = `,\nLimit(G(I*y), y=0, righ t) = limit(G(I*y), y=0, right);" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 257 "" 0 "" {TEXT 262 36 "Since the limits are NOT \+ the same, " }{XPPEDIT 18 0 "g(z) = exp(-1/z^2)" "6#/-%\"gG6#%\"zG-%$e xpG6#,$*&\"\"\"F-*$F'\"\"#!\"\"F0" }{TEXT 263 24 " is NOT continuous \+ at " }{XPPEDIT 18 0 "z = 0" "6#/%\"zG\"\"!" }{TEXT 268 22 " .\nREMARK . Although " }{XPPEDIT 18 0 "g(z)= exp(-1/z^2)" "6#/-%\"gG6#%\"zG-%$ expG6#,$*&\"\"\"F-*$F'\"\"#!\"\"F0" }{TEXT 264 132 " is known to be i nfinitely differentiable,\nit does not have a Maclaurin series expansi on. However, it does have a Laurent series.\n" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 126 "f:='f': p:='p': S:='S': z:='z':\nf := z -> exp(-1/z^ 2):\ns := z -> series(f(z), z=infinity, 14):\n`f(z) ` = f(z);\n`f(z) ` = s(z);" }}}{EXCHG {PARA 257 "" 0 "" {TEXT 265 19 "End of Section 7.5 ." }}}}{MARK "0 0 0" 27 }{VIEWOPTS 1 1 0 1 1 1803 1 1 1 1 } {PAGENUMBERS 0 1 2 33 1 1 }