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Matrix operations

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Samantha Steele
Samantha Steele 2011-9-20
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?
  1 个评论
the cyclist
the cyclist 2011-9-21
It would be really helpful if you could use the "code" button to format your question. It's really difficult to read.

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采纳的回答

bym
bym 2011-9-21
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?
  2 个评论
Walter Roberson
Walter Roberson 2011-9-21
why would (a 2x3) * (a 3x3) be an error? The inner dimensions agree.
Walter Roberson
Walter Roberson 2011-9-21
>> 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...

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更多回答（1 个）

Walter Roberson
Walter Roberson 2011-9-21
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.

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