{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 0 0 0 0 0 0 2 0 0 0 0 0 0 1 }{CSTYLE "Hyperlink" -1 17 "" 0 1 0 128 128 1 2 0 1 0 0 0 0 0 0 1 }{CSTYLE "2D Comment" 2 18 "" 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 256 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 257 "" 1 10 0 0 0 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 258 "" 1 10 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 259 "" 1 10 0 0 0 0 0 1 1 0 0 0 0 0 0 1 }{CSTYLE "" -1 260 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 261 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 262 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 263 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 264 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 265 "" 1 14 0 0 0 0 0 1 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 266 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 267 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 268 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 269 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 270 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 271 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 272 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 273 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 274 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 275 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 276 "Helvetica" 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 } {CSTYLE "" -1 277 "" 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 278 "Helvetica" 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 }{CSTYLE "" -1 279 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 280 "" 1 18 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 281 "" 1 14 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 282 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 283 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 284 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 285 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{CSTYLE "" -1 286 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 } {CSTYLE "" -1 287 "" 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 0 }{PSTYLE "Normal " -1 0 1 {CSTYLE "" -1 -1 "Times" 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 "Heading 2" -1 4 1 {CSTYLE "" -1 -1 "Times" 1 14 0 0 0 1 2 1 2 2 2 2 1 1 1 1 }1 1 0 0 8 2 1 0 1 0 2 2 0 1 }{PSTYLE "Heading 3" -1 5 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 1 1 2 2 2 2 1 1 1 1 }1 1 0 0 0 0 1 0 1 0 2 2 0 1 }{PSTYLE "Normal" -1 256 1 {CSTYLE "" -1 -1 "Times" 1 12 0 0 0 1 2 2 2 2 2 2 1 1 1 1 }3 1 0 0 0 0 1 0 1 0 2 2 0 1 }} {SECT 0 {EXCHG {PARA 256 "" 0 "" {TEXT -1 0 "" }{TEXT 279 0 "" }{TEXT 280 23 "Calculus IV with Maple\n" }{TEXT 281 32 "Copyright 2002, Dr. J ack Wagner\n" }{TEXT -1 30 "j.wagner@intelligentsearch.com" }}}{EXCHG {PARA 4 "" 0 "" {TEXT -1 58 "\nLesson 2: Vector Derivatives: grad, div , curl, laplacian\n" }}}{EXCHG {PARA 5 "" 0 "" {TEXT -1 0 "" }{TEXT 256 0 "" }{TEXT 257 0 "" }{TEXT 258 128 "Topics : Gradient, divergence , curl are illustrated and graphically interpreted. Laplacian defined. \nMaple commands introduced: " }{TEXT 259 56 "Gradient, Divergence, C url, Laplacian, fieldplot, evalVF" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "Gradient" 2 "Gradient" " " }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }{TEXT 260 11 "Example 2.1" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 5 "Let " } {XPPEDIT 18 0 "f = sin(x)-log(sin(y));" "6#/%\"fG,&-%$sinG6#%\"xG\"\" \"-%$logG6#-F'6#%\"yG!\"\"" }{TEXT -1 54 ". Compute and plot grad w. \+ We will plot level sets " }{XPPEDIT 18 0 "w^(-1);" "6#)%\"wG,$\"\"\" !\"\"" }{TEXT -1 1 "(" }{TEXT 266 1 "k" }{TEXT -1 26 ") , for k from 0 .1 to 1.0." }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 64 "restart: with (plots): with(LinearAlgebra): with(VectorCalculus):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 26 "f := sin(x) - log(sin(y));" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 27 "Plotting \+ ten level sets of " }{TEXT 287 7 "f(x, y)" }}}{EXCHG {PARA 0 "> " 0 " " {MPLTEXT 1 0 33 "S := seq(f - 1/k = 0, k = 1..10):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 66 "P1 := implicitplot(\{S\}, x = 3..3.5, y = 0..1.5, numpoints = 1000):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 37 "display(P1, scaling = constrained); \n" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 73 "The value of k represented by these curves increases from right to left. " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 " " 0 "" {TEXT -1 56 "Now compute the gradient at x = 3.3 on the level s et of " }{XPPEDIT 18 0 "f(x,y)=1/10" "6#/-%\"fG6$%\"xG%\"yG*&\"\"\"F* \"#5!\"\"" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 34 "gf := Gradient (f - 1/10, [x, y]);\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 41 "Y \+ := fsolve(subs(x = 3.3, f - 1/10), y);\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 26 "G := evalVF(gf, <3.3, Y>);" }}}{EXCHG {PARA 0 "" 0 " " {HYPERLNK 17 "evalVF" 2 "evalVF" "" }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 84 "Now we dr aw and plot a line through the point [3.3, .8832282346], and parallel \+ to G." }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 23 "N := <3.3, Y> + s \+ * G;\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 72 "P2 := plot([N[1], N[2], s = - 0.2..0.3], thickness = 2, color = black):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 40 "display(P1, P2, scaling = constrain ed);\n" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 308 "The gradient vector ap pears to pierce each of the level sets orthogonally to its tangent. I f this is so, then the gradient vector represents the shortest distan ce between successive level sets and, therefore, the most rapid change in the value of w. This is, in fact, true of any function in any dime nsion." }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 86 "We consider a surface o f arbitrary dimension represented by a level set of a map: F: " } {XPPEDIT 18 0 "R^n;" "6#)%\"RG%\"nG" }{TEXT -1 3 " ->" }{TEXT 267 1 "R " }{TEXT -1 4 " ; " }{TEXT 268 1 "f" }{TEXT -1 1 "(" }{XPPEDIT 18 0 " x[1];" "6#&%\"xG6#\"\"\"" }{TEXT -1 3 "..." }{XPPEDIT 18 0 "x[n];" "6# &%\"xG6#%\"nG" }{TEXT -1 6 ") = " }{TEXT 269 1 "K" }{TEXT -1 15 ", a nd a curve, " }{XPPEDIT 18 0 "gamma(t) = [x[1](t) .. x[n](t)];" "6#/-% &gammaG6#%\"tG7#;-&%\"xG6#\"\"\"6#F'-&F,6#%\"nG6#F'" }{TEXT -1 62 " \+ , imbedded in the surface, and passing through a point, " } {XPPEDIT 18 0 "p = x[1](t[0]) .. x[n](t[0]);" "6#/%\"pG;-&%\"xG6#\"\" \"6#&%\"tG6#\"\"!-&F(6#%\"nG6#&F-6#F/" }{TEXT -1 7 " . " } {XPPEDIT 18 0 "F(gamma(t)) = f(x[1](t) .. x[n](t));" "6#/-%\"FG6#-%&ga mmaG6#%\"tG-%\"fG6#;-&%\"xG6#\"\"\"6#F*-&F16#%\"nG6#F*" }{TEXT -1 3 " \+ = " }{TEXT 270 1 "K" }{TEXT -1 25 " Taking the gradient: " } {XPPEDIT 18 0 "grad(F(gamma(t)));" "6#-%%gradG6#-%\"FG6#-%&gammaG6#%\" tG" }{TEXT -1 12 " = grad F(" }{XPPEDIT 18 0 "gamma(t);" "6#-%&gamma G6#%\"tG" }{TEXT -1 1 " " }{XPPEDIT 18 0 "gamma;" "6#%&gammaG" }{TEXT -1 2 "'(" }{TEXT 271 1 "t" }{TEXT -1 16 ") = 0. Since " }{OLE 1 4160 1 "[xm]Br=WfoRrB:::wk;nyyI;G:;:j::>:B>N:F:nyyyyy]::yyyyyy:::::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::fyyyyya :nYf::G:jy;::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::JcvGYMt>^:fBWMtNHm=;:::::::n:;`:Z @[::JZDyBTk=XK[Aj;J:QZ:B:F:YLpfF>:::::::::J?NZ;vyyyyy=J:B:::::::c:;:=j [vGUMrvC?MoJ::::::::JCNZ;F:^:;jysy;Z::::::j:>:M=;:AB:Y:C:;:wyyN::wyyyq:W:YJ:><< JyKC>:a:c:e:wAyA:::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::=Z:yayQ:>:fl=JTD:?i:F:MZ=Fh;J;^J>:C:?R:f:FZb=V<;B:Gc;YJHvyyuy;B:UD:[Z:>ryM]yyyyY:H:GX:V[:JMJ@ fc[;>:[ll;B:;R:;b:D_mlVH[KR<:;B:::::::JFNZ;V:f:>Wlj:gml>:;:::::JJ:<::::::]J: :<:::::::::::::::::::vYxI:;Z:::::::::ICDMKUNZ ;>Z=fZ:JDJxAjDjw;<:[n:R:DZJ^DVH::C:Uk:^:>x;B:MB:;B:_;l;J:@Z:C:[q:F;;JSd:Z:vF;r:C>G;w I:UTRZ_gdOOXER:PZ>WdGSG@lQPnAMnQ@NbLYBxj]xoZHni@>YVKciDyDLcy]=D:<[:_xIHby?cnA\\IFbdve>we?_ xYgB@nAlj:F:=b:?b:?B:?B:=R:=j;@j:^:dj:BD\\L;Lj;M anOZ>NjcRD:>\\:B:qQBv:X;j ;::::::::::sB:;B:?JsXXtKPQYwJ:n@KM>QYwfZ;:RG<:::E=:t@:VDD`f;J]ZokB T:JJT>:C:j\\jj:Y;Bw[j]BN_Af<YVKd<>=tYKLBxjZ:xo\\RJZ:FZ BDj;K;RDJtDA<:::::::::::::::::::::::::::::::JhB:;: ;:::::::3:" }{TEXT -1 48 " is the principal part of the tangent vector to " }{OLE 1 4160 1 "[xm]Br=WfoRrB:::wk;nyyI;G:;:j::>:B>N:F:nyyyyy]:: yyyyyy:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::fyyyyya:nYf::G:jy;::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::::::::::::::::JcvGYMt>^:fBWMtNHm=;:::::::n:;`:Z@[::JZDyBTk=XK[Aj;J:QZ:B:F:YLpfF>:::::::::J?NZ;vyyyyy=J: B:::::::c:;:=j[vGUMrvC?MoJ::::::::JCNZ;F:^:;jysy;Z::::::j:>:M=;:AB:Y:C:;:wyyN::wyyyq:W:YJ:><:a:c:e:wAyA:::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::::::::::::=Z:yayQ:>:V_=JTD:kh:F:MZ=^g;J;FJ;B:;J^;UTR:;Jbf:D:;b:E:cb:;U:wjDjwEJ:uI<:[V:D_mlVH[KRJ:<:::::::>=?R: A:EZ:vYxY:>Z::::::J::::::;C:?jysy:>:< ::::::]J:@:<::::::::::::vYxI:;Z::::::::::::::::::::yay=J:B::::::::J N`L;@Z=fZ:JDJHAjDjw;<:[n:R:DZJ^DVH::C:Uk:^:>x;B:MB:;B:_;l;J:@Z:C:[q:F;;JSd:Z:vF;r:=> G;kq`@@jdPOpgZ;R;Lncp^oB:arOMeU=dMaTL@kARKeuR:Dpqr>EVjnCW?B;?VD `\\:V;:Sjysy=:;:[B::sg:Gsytom<@:ZoB:::fF:bU:jcbRl`M:nBRWF\\@:> ^@;J<:fBFFjQ:LYBvBH^;kAQ^dZID:<[:kZxQ^>\\IFBZYgB@>B:=b:DJ; <:=:A:CZDB::BDj;K;RDJ:<:::::::::::::::::::::::::::::::::::::::::5:" } {TEXT -1 8 ", grad " }{TEXT 272 1 "F" }{TEXT -1 1 "(" }{XPPEDIT 18 0 "gamma;" "6#%&gammaG" }{TEXT -1 1 "(" }{TEXT 273 1 "t" }{TEXT -1 46 ") ) is orthogonal to the tangent to the curve " }{XPPEDIT 18 0 "gamma(t );" "6#-%&gammaG6#%\"tG" }{TEXT -1 155 " at p. But every tangent to t he surface at p, is the tangent to a curve, (existence theorem for so lution of first order differential equations) so grad " }{TEXT 274 1 "F" }{TEXT -1 1 "(" }{XPPEDIT 18 0 "gamma;" "6#%&gammaG" }{TEXT -1 1 " (" }{TEXT 275 1 "t" }{TEXT -1 170 ")) is orthogonal to the tangent pl ane at p. The gradient vector represents the direction and magnitude \+ of the greatest change in F, at the point where it is evaluated. " }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 52 "Th is can be illustrated easily in three dimensions. " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 261 11 "Example 2.2" }} {PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 5 "Le t " }{OLE 1 4168 1 "[xm]Br=WfoRrB:::wk;nyyI;G:;:j::>:B>N:F:nyyyyy]::y yyyyy::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::fyyyyya:nYf::G:jy;:::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::::::JcvGYMt>^:fBWMtNHm=;:::::::n:;`:Z@[::Jj]qCTk=XK[Aj;J:QZ:B:F:YLpfF>:::::::::J?NZ;vyyyyy=J:B :::::::c:;:=j[vGUMrvC?MoJ::::::::JCNZ;F:f:vYxY:B::::::F:;jnJ:j;::::::::N<;;j>J?>:Q:S:U J:n;;jA>:[Z:F:AR:=r:dj:Dk;i^AfXDJ=EKKD k;]a=v;hjB@J;\\RSJ?DJ=i\\LVjss:Y:::DJ>M]LVjrc>AVXr:OX:;J;FOZ: >Z::::::J@>Z::::::::kJ;@j;>:C:yayA:<::::::G:Wx:B:: ::::::::::jysy:>:<:::::::::::::::::::vYxI:;Z:::::::::UD:[Z:>rymTyyyyYJ t:eY:V[:JMJ@fc[;PP:D:;b:E:cb:cqjTjD>:qi:?syB:>l;B:;R:;b::_cFis:sW:E:cJJAJnijD>:qQ:uI;B :>L:W<:^:f?=J:_cl;F:;R:D:js ::^::C:[q:>\\:>Z:N@B:G:QdXkUXkUX_r:Sd:]s:Qy:K_=B:^<>r;^>c; fc[_HjdPOX@j<@Z?BKaTMP=arOMeU=dMaTL@k^@Oh[;^Z?gh];EDXceV=MC@lQPnAMnQ@NbLYBxj]xoZHni@>YVKciDyDLcy]=D:<[:_xIHby?cnA\\IFbdve>we?_x YgB@nAlj:F:=b:?b:?B:?B:=R:=j;@j:VjtcX?B;Gf>? SE?B;\\arW:sJ:hj:@j:N:KfFD=Ob:CjOV_<^Z=HImu:;BA::::KFGLM;Lj;]A?B;AVX>Z :V[::^;yayI:;B:;:[B:Z:FZ:C:[q:: ::::::::::::::::::::::::::::::::::::::::::::5:" }{TEXT -1 108 " . Com pute and plot the gradient vector.\nDefine an implicit function of (x, y, z) for various values of K.\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 81 "restart: with(plots): with(LinearAlgebra):with(Vector Calculus): with(plottools):\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 39 "F := K ->z - x^2 + y^2 + 4 * x * y - K:" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 44 "v := [x, y, z]: gradF := Gradient(F(0), v);\n" } }}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 151 "We could equally well have taken any value of K. 0 happens to be conv enient because it gives simple integer values for the components of t he gradient." }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 18 "p := <1, 1, - 4>:" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 115 "gF[1, 1, - 4] \+ := evalVF(gradF, p); #The gradient vector at (1, 1, - 4)\n \+ " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 31 "G := p + s * gF[1, 1, - 4]; \011\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 88 "P1 := spacecurve(evalm(G), s = - .2..0.25, color \+ = black, thickness = 2, axes = boxed):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 139 "S := seq(implicitplot3d(F(5 * k), x = 0..2, y = 0..2 , \nz = - 5.. - 2, style = wireframe, color = pink, grid = [12, 12, 12]), k = 0..3):\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 66 "disp lay(S, P1, scaling = constrained, orientation = [ - 20, 65]);\n" }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 92 "The gradient vector appears to be \+ orthogonal to each of the level sets.\n " }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 277 "Without presenting any mathematic al justification (although ample justification exists), we will operat e with the gradient vector operator as if it were an ordinary vector; \+ we will take both the dot product and the crossproduct of del with o rdinary vectors and with itself. " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 53 " The curl of a vector V is defined by: curl(V) = del" }{TEXT 276 1 "x" }{TEXT -1 1 "V" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 64 "restart: with(LinearAlgebra): with(VectorCalculus):with(linalg):" }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 90 "Th ere are two defined forms of the curl in Maple. One, spelled with a sm all \"c\" is in the " }{TEXT 282 6 "linalg" }{TEXT -1 82 " package and operates on vectors; the other, spelled with a capital \"C\" is in th e " }{TEXT 283 14 "VectorCalculus" }{TEXT -1 39 " package and operates on vector fields." }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "curl" 2 "c url" "" }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "Cur l" 2 "Curl" "" }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 87 "V := VectorField(, 'cartesian'[x, y, z]); " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 9 "Curl(V);\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 68 "V1 := [v[1](x, y, z), v[2](x, y, z), v[3](x, y, z)];r := [x, y, z] :\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 12 "curl(V1, r);" }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 131 "T o have an idea of what this means, consider a vector field, that is, a function that assigns a vector to each point in the domain." }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 262 11 "E xample 2.3" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 6 " Let " }{TEXT 277 0 "" }{XPPEDIT 18 0 "F(x,y) = [x^2*y, y ^2*x, x^2-y^2];" "6#/-%\"FG6$%\"xG%\"yG7%*&F'\"\"#F(\"\"\"*&F(F+F'F,,& *$F'F+F,*$F(F+!\"\"" }{TEXT -1 61 " Take the curl of this vector \+ field and fieldplot both. " }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "fieldplot" 2 "fieldplot" "" }{MPLTEXT 1 0 2 " " }{HYPERLNK 17 "fieldplot3d" 2 "fieldplot3d" "" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 76 "restart: with(LinearAlgebra): with( VectorCalculus):with(linalg):with(plots):" }}}{EXCHG {PARA 0 "> " 0 " " {MPLTEXT 1 0 45 "F := (x, y) ->:\n" }}} {EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 8 "F(x, y);" }}}{EXCHG {PARA 0 " > " 0 "" {MPLTEXT 1 0 36 "curl_F := curl(F(x, y), [x, y, z]);\n" }}} {EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 136 "f1 := fieldplot3d(F(x, y), \+ x = - 10..10, y = - 10..10, z = \n - 10..10, axes = framed, color = \+ red, arrows = THICK, grid = [3, 3, 3]):\n" }}}{EXCHG {PARA 0 "> " 0 " " {MPLTEXT 1 0 137 "f2 := fieldplot3d(curl_F, x = - 10..10, y = - 10 ..10, \nz = - 10..10, axes = framed, color = black, arrows = THICK, g rid = [3, 3, 3]):\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 17 "disp lay(f1, f2);\n" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 502 "If the origina l vector field F, (thick arrows) represents the velocity of fluid flow in a container, then curl F (the thinner arrows) is the torque exerte d by the fluid, both in magnitude and direction, (determined by the ri ght hand rule). If any group of thick vectors is rotated into an adj acent group and the fingers of the right hand curled in the direction \+ of rotation, the thumb of the right hand will point in the direction o f the thinner vectors (the torque) situated between the two groups. " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 39 "Now formally defining the vector field." }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 49 "FF := VectorField(F(x, y), 'cartesian'[x, y, z]);" }} }{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 16 "CFF := Curl(FF);" }}} {EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 131 "P3 := fieldplot3d(FF, x = \+ - 10..10, y = - 10..10, z = \n - 10..10, axes = framed, color = red, \+ arrows = THICK, grid = [3, 3, 3]):\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 134 "P4 := fieldplot3d(CFF, x = - 10..10, y = - 10..10, \nz = - 10..10, axes = framed, color = black, arrows = THICK, grid = [3, 3, 3]):\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 16 "display(P 3, P4);" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 19 "The alternative to " } {TEXT 286 4 "Curl" }{TEXT -1 1 "." }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 10 "Del &x FF;" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" } }{PARA 0 "" 0 "" {TEXT -1 69 "Note that, because of the equality of mi xed partial derivatives, del" }{TEXT 278 1 "x" }{TEXT -1 9 "del = 0. \+ " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 27 "del := ; " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 11 "del &x del;" }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 290 "Since we are considering del as a vector we may also take the \+ dot product of del with a vector, V. This is known as the divergence \+ of V. Again there are two definitions, Divergence and diverge in the \+ VectorCalculus and linalg packages, operating on vector fields and vec tors respectively." }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "Divergence " 2 "Divergence" "" }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "diverge" 2 "diverge" "" }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 79 "restart: with(linalg): with(LinearA lgebra): with(VectorCalculus): with(plots):\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 65 "V := (x, y, z) -> : " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 52 "VV := \+ VectorField(V(x, y, z), 'cartesian'[x, y, z]);" }}}{EXCHG {PARA 0 "> \+ " 0 "" {MPLTEXT 1 0 15 "Divergence(VV);" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 52 "V1 := [v[1](x, y, z), v[2](x, y, z), v[3](x, y, z)]; " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 23 "diverge(V1, [x, y, z]); " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 215 "To have a picture of what this might mean, suppose we consider F \+ as the velocity field of some gas. That is, F is a vector field repre senting the velocity of the gas particles (assumed to be uniform) at e ach point." }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT 263 11 "Example 2.4" }}{PARA 0 "" 0 "" {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 32 "Find and plot the divergence of " }{OLE 1 4164 1 "[xm]Br=WfoRrB:::wk;nyyI;G:;:j::>:B>N:F:nyyyyy]::yyyyyy:::::: :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::fyyyy ya:nYf::G:jy;::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::::::::::::::JcvGYMt>^:fBWMtNHm=;:::::::n:;` :Z@[::JJTRETk=XK[Aj;J:T:<:=ja^GE=;:::::::::N;?R:yyyyyy:>:<::::::JDJ:j: VBYmp>HYLkNG>::::::::N::::: :::N<;F;N;;j?J@j@>:W:YJ:><:a:c:e:gJ:v<R<:TNEj`@Pt\\Pd` QrPPJPMQWdG_dnBwmcf]]:>::::::V:>: :::::::::^=NZ:vo`aI>:>\\yGCsVVM<;j;@j:HZDFZLVj@c:?fHDJ=q]AFXHjAr <]R:?B\\_;Ob>AVXDJ;m\\LVjss:Y::Zrc:?>\\a=::b:Gf>?c>AVX::J;q?lr^J:::::: :vYxy;<:C:=J:vYxY;J:jI<[:Vir:WY:N:E@;J::::::;C:?B:yay=J:>Z::::::J=?R:A J:^:vYxY:B::::::v:n\\>Z:::::::::::::yay=J:B:::::::::::::::::::jysy:>:< ::::::::=j:;B:E:Sb:;d:;g=a:Gc;YJHvyyuy;B :UD:[Z:>rymTyyyyYjt:eY:V[:JMJ@fc[;PP:D:Djfn;^m;fZ:JBC:;R:D::::C:Uk:^:>x;B:YJ:N`DZ:f:NaU__ffE[W:yg:E h:CS;Hj<<:c:GlDjw;<:[n:>Z;b::a=:J:C:[Y:=JCL;B:;R:D:ETWAEUMES;sNmMkxPpFZ:^:f?=JWdGSGARKeuR:Dpqr>EHni@>YVKciDyD Lcy]=D:<[:_xIHby?cnA\\IFbdve>we?_xYgB@nAlj:F:=b:?b:?B:?j:@j:VZ;FZ:^:dj :NjtbH?B;GVIpM;LJ;i_UOZ>VjrCXAJH>ZEFZ;F:?J>E]lJ?DJ:>\\ :B:qQBv:>:sg:X=B:AB: " 0 "" {MPLTEXT 1 0 64 "re start: with(plots): with(LinearAlgebra): with(VectorCalculus):" }}} {EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 45 "F := (x, y) ->[x^2 * y, y^2 \+ * x, x^2 - y^2]:\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 51 "FF := VectorField(, 'cartesian'[x, y, z]);" }}}{EXCHG {PARA 0 "> \+ " 0 "" {MPLTEXT 1 0 24 "Div_F := Divergence(FF);" }}}{EXCHG {PARA 0 " " 0 "" {TEXT -1 197 "The divergence is a scalar quantity. If we const ruct a vector parametrized by x and y with div_F as the z coordinate, \+ we will obtain a surface representing div F at each point in the x - \+ y plane." }{MPLTEXT 1 0 1 " " }{TEXT -1 1 " " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 23 "G := ;" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 30 "We now plot G together with F." }}}{EXCHG {PARA 0 "> \+ " 0 "" {MPLTEXT 1 0 90 "P1 := plot3d(G, x = - 2..2, y = - 2..2, axes = framed, color = blue, style = wireframe):" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 144 "P2 := fieldplot3d(F(x, y), x = - 2..2, y = - \+ 2..2, z = \n - 2..2, axes = framed, color = pink, color = red, arrows \+ = THICK, grid = [5, 5, 2]):\n" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 17 "display(P1, P2);\n" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 382 " The surface div V represents the flux of gas out of a unit cube. Observe that where the arrows point inward, the flux is negative, gas partic les accumulate in the cube; the density of the gas rises. Where the a rrows point outward, the flux is positive, the density of gas particle s in the cube is diminishing. div F therefore measures the change in d ensity of gas in the cube. " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 83 "div(grad) is defined and is an operator of the greatest importance: the Laplacian. " }}}{EXCHG {PARA 0 "" 0 " " {TEXT -1 66 "Maple does not have a way to input partial differential operators." }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 27 "del := ; " }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 16 "Lap := d el.del;\n" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 51 "The Laplacian functi on, is however, defined in the " }{TEXT 284 6 "linalg" }{TEXT -1 17 " \+ package and the " }{TEXT 285 14 "VectorCalculus" }{TEXT -1 9 " package ." }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "laplacian" 2 "laplacian" " " }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "" 0 "" {HYPERLNK 17 "Laplacian " 2 "Laplacian" "" }{MPLTEXT 1 0 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}{PARA 0 "" 0 "" {TEXT -1 113 "Grad, curl and div figure larg ely in physical applications and will all be looked at more closely as we proceed. " }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }{TEXT 264 0 " " }{TEXT 265 8 "Practice" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 0 "" }}} {EXCHG {PARA 0 "" 0 "" {TEXT -1 67 "1. Plot each of the following vect or fields together with its curl." }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 4 "a. " }{XPPEDIT 18 0 "F(x,y) = [x+y, x-y, x*y];" "6#/-%\"FG6$%\"xG% \"yG7%,&F'\"\"\"F(F+,&F'F+F(!\"\"*&F'F+F(F+" }}}{EXCHG {PARA 0 "" 0 " " {TEXT -1 3 "b. " }{XPPEDIT 18 0 "F(x,y) = [-x/(x^2+y^2), y/(x^2+y^2) , 1/(x^2+y^2)];" "6#/-%\"FG6$%\"xG%\"yG7%,$*&F'\"\"\",&*$F'\"\"#F,*$F( F/F,!\"\"F1*&F(F,,&*$F'F/F,*$F(F/F,F1*&F,F,,&*$F'F/F,*$F(F/F,F1" } {TEXT -1 0 "" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 3 "c. " }{XPPEDIT 18 0 "F(x,y) = [sin(x+y), cos(x+y), x+y];" "6#/-%\"FG6$%\"xG%\"yG7%-%$sin G6#,&F'\"\"\"F(F.-%$cosG6#,&F'F.F(F.,&F'F.F(F." }{TEXT -1 0 "" }}}} {MARK "0 0 2" 0 }{VIEWOPTS 1 1 0 1 1 1803 1 1 1 1 }{PAGENUMBERS 0 1 2 33 1 1 }