Matrix operations

So i am having trouble with one of my homework problems..

i am given matrices

A=[1,21,3;5,7,9;11,12,32];
B=[2,3,4;5,8,11;8,9,22];
C=[2,3,4;7,9,11];

and need to perform the following operations:

inv(A)
A*inv(A)
A*A'
A.*B
A.*C %need help here%
%multiplication%
A=[1,21,3;5,7,9;11,12,32];
B=[2,3,4;5,8,11;8,9,22];
C=[2,3,4;7,9,11];
A*B;
B*A;
A*C;%and here%
C*A%and here%

but for the marked locations matlab gives me an error message.. what can i do differently?

[the cyclist]

It would be really helpful if you could use the "code" button to format your question. It's really difficult to read.

Answer 1

[bym]

A is size 3x3, C is size 2x3, therefore:

A.*C
A*C
C*A

are all errors because of dimensions. Without further information you can't do anything differently. Perhaps that was the goal of the assignment?

[Walter Roberson]

why would (a 2x3) * (a 3x3) be an error? The inner dimensions agree.

[Walter Roberson]

>> A=[1,21,3;5,7,9;11,12,32];

>> C=[2,3,4;7,9,11];

>> C*A

ans =

61 111 161

173 342 454

Doesn't look like an error to me...

Answer 2

[Walter Roberson]

I would expect errors for A.*C and A*C, but I would not expect an error for C*A: I would expect a 2 x 3 matrix as the result.