Análisis Matemático IV 

Problemas de integrales dobles y triples 

I. Marrero 

Curso 2007/08 

 

> restart:
 

> with(plots):
 

> read "calcplot2.txt";
 

>
 

Integrales dobles - Problema 13 

> f:=x*y;
 

`*`(x, `*`(y)) (1.1)
 

> domy:=y=0..2;
 

y = 0 .. 2 (1.2)
 

> domx:=x=y-2..3*sqrt(4-y^2)/2;
 

x = `+`(y, `-`(2)) .. `+`(`*`(`/`(3, 2), `*`(`^`(`+`(4, `-`(`*`(`^`(y, 2)))), `/`(1, 2))))) (1.3)
 

> Int( Int(f, domx), domy) = int( int( f, domx), domy);
 

Int(Int(`*`(x, `*`(y)), x = `+`(y, `-`(2)) .. `+`(`*`(`/`(3, 2), `*`(`^`(`+`(4, `-`(`*`(`^`(y, 2)))), `/`(1, 2)))))), y = 0 .. 2) = `/`(23, 6) (1.4)
 

> Dxy := dxdyplot( domx, domy ): display(Dxy, axes=normal,labels=[`eje x`,`eje y`],tickmarks=[3,3]);
 

Plot_2d
 

>
 

Integrales dobles - Problema 20 

(a)  

> f:=r*(1+r^2)^(-3/2);
 

`/`(`*`(r), `*`(`^`(`+`(1, `*`(`^`(r, 2))), `/`(3, 2)))) (2.1.1)
 

> domr:=r=0..1/cos(theta);
 

r = 0 .. `/`(1, `*`(cos(theta))) (2.1.2)
 

> domt:=theta=0..Pi/4;
 

theta = 0 .. `+`(`*`(`/`(1, 4), `*`(Pi))) (2.1.3)
 

> Int( Int(f, domr), domt) = int( int(f, domr), domt);
 

Int(Int(`/`(`*`(r), `*`(`^`(`+`(1, `*`(`^`(r, 2))), `/`(3, 2)))), r = 0 .. `/`(1, `*`(cos(theta)))), theta = 0 .. `+`(`*`(`/`(1, 4), `*`(Pi)))) = `+`(`*`(`/`(1, 12), `*`(Pi))) (2.1.4)
 

> Drt := drdtplot( domr, domt ): display(Drt, axes=normal,labels=[`eje x`,`eje y`],tickmarks=[3,3]);
 

Plot_2d
 

>
 

 

(b) 

> f:=r^4*(cos(theta)^3+sin(theta)^3);
 

`*`(`^`(r, 4), `*`(`+`(`*`(`^`(cos(theta), 3)), `*`(`^`(sin(theta), 3))))) (2.2.1)
 

> domr:=r=2*cos(theta)..1;
 

r = `+`(`*`(2, `*`(cos(theta)))) .. 1 (2.2.2)
 

> domt:=theta=Pi/3..Pi/2;
 

theta = `+`(`*`(`/`(1, 3), `*`(Pi))) .. `+`(`*`(`/`(1, 2), `*`(Pi))) (2.2.3)
 

> Int( Int(f, domr), domt) = int( int(f, domr), domt);
 

Int(Int(`*`(`^`(r, 4), `*`(`+`(`*`(`^`(cos(theta), 3)), `*`(`^`(sin(theta), 3))))), r = `+`(`*`(2, `*`(cos(theta)))) .. 1), theta = `+`(`*`(`/`(1, 3), `*`(Pi))) .. `+`(`*`(`/`(1, 2), `*`(Pi)))) = `+`(... (2.2.4)
 

> Drt := drdtplot( domr, domt ): display(Drt, axes=normal,labels=[`eje x`,`eje y`],tickmarks=[3,3]);
 

Plot_2d
 

>
 

 

Integrales triples - Problema 11 

> f:=1-x-y-z;
 

`+`(1, `-`(x), `-`(y), `-`(z)) (3.1)
 

> domz:=z=0..1-x-y;
 

z = 0 .. `+`(1, `-`(x), `-`(y)) (3.2)
 

> domy:=y=0..1-x;
 

y = 0 .. `+`(1, `-`(x)) (3.3)
 

> domx:=x=0..1;
 

x = 0 .. 1 (3.4)
 

> Int( Int( Int(f, domz), domy), domx) = int( int( int(f, domz), domy), domx);
 

Int(Int(Int(`+`(1, `-`(x), `-`(y), `-`(z)), z = 0 .. `+`(1, `-`(x), `-`(y))), y = 0 .. `+`(1, `-`(x))), x = 0 .. 1) = `/`(1, 24) (3.5)
 

> Dzyx := dzdydxplot( domz, domy, domx ): display(Dzyx, axes=normal,labels=[`eje x`,`eje y`,`eje z`],tickmarks=[3,3,3]);
 

Plot
 

>
 

Integrales triples - Problema 16 

(a) 

> f:=r^5;
 

`*`(`^`(r, 5)) (4.1.1)
 

> domz:=z=r^2/2..2;
 

z = `+`(`*`(`/`(1, 2), `*`(`^`(r, 2)))) .. 2 (4.1.2)
 

> domr:=r=0..2;
 

r = 0 .. 2 (4.1.3)
 

> domt:=theta=0..2*Pi;
 

theta = 0 .. `+`(`*`(2, `*`(Pi))) (4.1.4)
 

> Int( Int( Int(f, domz), domr), domt) = int( int( int(f, domz), domr), domt);
 

Int(Int(Int(`*`(`^`(r, 5)), z = `+`(`*`(`/`(1, 2), `*`(`^`(r, 2)))) .. 2), r = 0 .. 2), theta = 0 .. `+`(`*`(2, `*`(Pi)))) = `+`(`*`(`/`(32, 3), `*`(Pi))) (4.1.5)
 

> Dzrt := dzdrdtplot( domz, domr, domt ): display(Dzrt, axes=normal,labels=[`eje y`,`eje x`,`eje z`],tickmarks=[3,3,3],orientation=[39,72]);
 

Plot
 

>
 

 

(b) 

> f:=z*exp(-r^2)*r;
 

`*`(z, `*`(exp(`+`(`-`(`*`(`^`(r, 2))))), `*`(r))) (4.2.1)
 

> domz:=z=sqrt(2)*r..sqrt(r^2+1);
 

z = `*`(`^`(2, `/`(1, 2)), `*`(r)) .. `*`(`^`(`+`(`*`(`^`(r, 2)), 1), `/`(1, 2))) (4.2.2)
 

> domr:=r=0..1;
 

r = 0 .. 1 (4.2.3)
 

> domt:=theta=0..2*Pi;
 

theta = 0 .. `+`(`*`(2, `*`(Pi))) (4.2.4)
 

> Int( Int( Int(f, domz), domr), domt) = int( int( int(f, domz), domr), domt);
 

Int(Int(Int(`*`(z, `*`(exp(`+`(`-`(`*`(`^`(r, 2))))), `*`(r))), z = `*`(`^`(2, `/`(1, 2)), `*`(r)) .. `*`(`^`(`+`(`*`(`^`(r, 2)), 1), `/`(1, 2)))), r = 0 .. 1), theta = 0 .. `+`(`*`(2, `*`(Pi)))) = `+... (4.2.5)
 

> Dzrt := dzdrdtplot( domz, domr, domt ): display(Dzrt, axes=normal,labels=[`eje y`,`eje x`,`eje z`],tickmarks=[3,3,3],orientation=[39,63]);
 

Plot
 

>
 

Integrales triples - Problema 20 

(a)  

> f:=rho^5*sin(phi)^3*cos(phi)*cos(theta)*sin(theta);
 

`*`(`^`(rho, 5), `*`(`^`(sin(phi), 3), `*`(cos(phi), `*`(cos(theta), `*`(sin(theta)))))) (5.1.1)
 

> domp:=rho=0..1;
 

rho = 0 .. 1 (5.1.2)
 

> domphi:=phi=0..Pi/2;
 

phi = 0 .. `+`(`*`(`/`(1, 2), `*`(Pi))) (5.1.3)
 

> domt:=theta=0..Pi/2;
 

theta = 0 .. `+`(`*`(`/`(1, 2), `*`(Pi))) (5.1.4)
 

> Int( Int( Int(f, domp), domphi), domt)= int( int( int(f, domp), domphi), domt);
 

Int(Int(Int(`*`(`^`(rho, 5), `*`(`^`(sin(phi), 3), `*`(cos(phi), `*`(cos(theta), `*`(sin(theta)))))), rho = 0 .. 1), phi = 0 .. `+`(`*`(`/`(1, 2), `*`(Pi)))), theta = 0 .. `+`(`*`(`/`(1, 2), `*`(Pi)))... (5.1.5)
 

> Drpt := dpdphidtplot( domp, domphi, domt ): display(Drpt, axes=normal,labels=[`eje x`,`eje y`,`eje z`],tickmarks=[3,3,3],orientation=[-24,57]);
 

Plot
 

>
 

(b) 

> a:='a';
 

a (5.2.1)
 

> f:=rho^4*sin(phi);
 

`*`(`^`(rho, 4), `*`(sin(phi))) (5.2.2)
 

> domp1:=rho=2*a*cos(phi)/sin(phi)^2..sqrt(3)*a;
 

rho = `+`(`/`(`*`(2, `*`(a, `*`(cos(phi)))), `*`(`^`(sin(phi), 2)))) .. `*`(`^`(3, `/`(1, 2)), `*`(a)) (5.2.3)
 

> domphi1:=phi=arccos(1/sqrt(3))..Pi/2;
 

phi = arccos(`+`(`*`(`/`(1, 3), `*`(`^`(3, `/`(1, 2)))))) .. `+`(`*`(`/`(1, 2), `*`(Pi))) (5.2.4)
 

> domt1:=theta=0..2*Pi;
 

theta = 0 .. `+`(`*`(2, `*`(Pi))) (5.2.5)
 

> domp2:=rho=0..sqrt(3)*a;
 

rho = 0 .. `*`(`^`(3, `/`(1, 2)), `*`(a)) (5.2.6)
 

> domphi2:=phi=Pi/2..Pi;
 

phi = `+`(`*`(`/`(1, 2), `*`(Pi))) .. Pi (5.2.7)
 

> domt2:=theta=0..2*Pi;
 

theta = 0 .. `+`(`*`(2, `*`(Pi))) (5.2.8)
 

> Int( Int( Int(f, domp1), domphi1), domt1)+Int( Int( Int(f, domp2), domphi2), domt2)=int( int( int(f, domp1), domphi1), domt1)+int( int( int(f, domp2), domphi2), domt2);
 

`+`(Int(Int(Int(`*`(`^`(rho, 4), `*`(sin(phi))), rho = `+`(`/`(`*`(2, `*`(a, `*`(cos(phi)))), `*`(`^`(sin(phi), 2)))) .. `*`(`^`(3, `/`(1, 2)), `*`(a))), phi = arccos(`+`(`*`(`/`(1, 3), `*`(`^`(3, `/`...
`+`(Int(Int(Int(`*`(`^`(rho, 4), `*`(sin(phi))), rho = `+`(`/`(`*`(2, `*`(a, `*`(cos(phi)))), `*`(`^`(sin(phi), 2)))) .. `*`(`^`(3, `/`(1, 2)), `*`(a))), phi = arccos(`+`(`*`(`/`(1, 3), `*`(`^`(3, `/`...
(5.2.9)
 

> a:=4;
 

4 (5.2.10)
 

> Drpt1 := dpdphidtplot( domp1, domphi1, domt1 ):
Drpt2 := dpdphidtplot( domp2, domphi2, domt2 ):
display({Drpt1,Drpt2}, axes=normal,labels=[`eje y`,`eje x`,`eje z`],tickmarks=[3,3,3]);
 

Plot
 

>