syms theta phi
r = [2.*sin(phi).*cos(theta) 2.*sin(phi).*sin(theta) 2.*cos(phi)];
P=diff(r,theta);
R=diff(r,phi);
C = cross(R,P)
Why not try simplify? It might work.
C = simplify(C)
So a simplify helped. Never assume that ALL computations end with a simplfy.
Norm can introduce some problems, because norm feels the need to introduce an absolute value in there.
norm(C)
But what is the 2-norm of a vector, but a sum of squares of elements, and then a sqrt?
normsquared = simplify(sum(C.^2))
And that is getting pretty close.
sqrt(normsquared)
And there is still a minor problem here, probably because MATLAB is not certain that sin(phi)^2 is a positive number. We can tell it that, by telling MATLAB that phi is itself real valued.
assume(phi,'real')
simplify(sqrt(normsquared))
That seems reasonable now. Symbolic tools just need a little gentle persuasion at times.
