How to carry out this multiplication.

syms fyi theta x y z
r = 2;
x = r*sin(fyi)*cos(theta);
y = r*sin(fyi)*sin(theta);
z = r*cos(fyi);
a = [x y z]
simplify(subs((x^2)+(y^2)+z^2,[x,y,z],a))
ezsurf(a(1),a(2),a(3),[0,pi,0,2*pi])
surffactor = simple((cross(diff(a,theta),diff(a,fyi))))

here i get the surffactor a symbolic matric of 1*3 . I need to multiply this witha nother matrix of 101*7000 which has constant entities. How should i carry out the multiplication. it shows error

Error in MuPAD command: Dimensions do not match. [(Dom::Matrix(Dom::ExpressionField()))::_mult2]

Error in sym/privBinaryOp (line 1694)
            Csym = mupadmex(op,args{1}.s, args{2}.s, varargin{:});

Error in sym/mtimes (line 184)
        X = privBinaryOp(A, B, 'symobj::mtimes');

Error in code (line 42)
majorfunction = (func1*surffactor1)

Answer 1

[Walter Roberson]

What size of output are you expecting when you multiply your 1 x 3 matrix by a 101*7000 matrix? The dimensions do not agree.

Are you sure it is cross product you want and not dot product? Dot product would give you a scalar rather than a vector.

[Chandramohan Meena]

I could make my 1*3 symbolic matrix into 1*7000 by padding zeroes, then dimesions will agree but it still isn't working. And yeah it is cross product only.

[Walter Roberson]

func1(:,1:3) * surffactor1

if you are looking for a 101 x 1 answer. If you are not looking for a 101 x 1 answer then please indicate exactly what size of output you are looking for.