Problem Find area surface

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justin Taylor 2011-12-18

x = ( 1-u )(3+cos v)cos(2pi*u)

y = ( 1-u )(3+cos v)sin(2pi*u)

z = 4u + ( 1-u )sinv.

D={(u,v)|0<=u<=1,0<=v<=2pi}

mycode

{ syms u v;

x = (1-u).*(3+cos(v)).*cos(pi*u);

y = (1-u).*(3+cos(v)).*sin(pi*u);

z = 8*u+( 1-u ).*sin(v);

F=[x,y,z];

ru=diff(F,[u]);

rv=diff(F,[v]);

ruv=ru.*rv;

druv=sqrt(ruv(1).^2+ruv(2).^2+ruv(3).^2);

S=int(int(druv,u,0,1),v,0,2*pi)

}

bym 2011-12-18

you are going to need:

a =feval(symengine,'linalg::crossProduct',ru,rv)%  .* is not cross product!
b =feval(symengine,'norm',a,2)

once you get the integrand (b) then I would suggest you evaluate it numerically rather than symbolically. You can use

MatlabFunction()

to turn it into a function to pass to

dblquad

bym 2011-12-19

the expression is for the _cross_ product not _dot_ product.

Walter Roberson 2011-12-20

Some day I will learn, "Never feed them after Midnight". ;-)

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