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# Vector Math help

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I have two vectors a8,10,9) b7,3,5) Would the following statement be true.. ? --> Transpose(a)*(a) == (a)*transpose(a) ? how would I work out det(a * transpose(a)) ? any help with this will be helpful thanx also any links that would help would also be useful thanx

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Looks like homework...

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Yeah... Look into matrix properties, or, more simply, do it yourself! Multiplying and transposing matrices is easy. If you arrive to the same results on both sides of the equation, then there is 99% chance that the property holds in general.

Cédric

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Please let us know why you are asking this particular question in this forum.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

No and zero.

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Try looking it up in your linear algebra book. If you don''t have one, try a library.

However, as a hint, this relation is extremely easy to figure out. First way, use the rules for the multiplication of two matrices inside the determinant operator. Second, just step back and think for a second about commutativity, and what a*a^T must be for that relation to be true.

And the answer is not zero.

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thnx for the help (sorta)...
i STFW and got no help initally so went and checked out the libary, I quickly found 4-5 good references.

Lesson learnt... never take the easy way out, as it usually turns out to be one of the most difficult anyway ...

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The left side is a 1 x 1 matrix and the right is a 3 x 3 matrix so they can''t be equal. The columns of the right side are all multiples of one another so the determinant must be zero.

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Oh, I missed the first part, where a was given. I thought that the given was: Transpose(a)*(a) == (a)*transpose(a), in which case the determinant is not zero.

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Closing thread since no reference to game development given.

Graham Rhodes
Senior Scientist
Applied Research Associates, Inc.

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