How Do You Prove Matrices Like AA^T and A+A^T Are Symmetric?

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The discussion focuses on proving that the matrices AA^T and A+A^T are symmetric. It is established that for a square matrix A, the transpose of the sum (A+B)^T equals A^T + B^T, and the transpose of the product (AB)^T equals B^T A^T. By applying these properties, one can directly show that both AA^T and A+A^T are symmetric matrices, confirming that A^T = A for symmetric matrices.

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FlyingDonkey
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I'm having trouble understanding a certain matrix problem.

-Show that AA^T and A^TA are symmetric.
-Show that A+A^T is symmetric.

Any help would be greatly appreciated.
 
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Showing A+AT is symmetric should be trivial... write out A as an nxn matrix (it needs to be square for addition to be defined!) with entries a_{i,j}, and you should be able to calculate directly the i,jth entry of A+AT
 
Symmetric means A^T=A. And you know that (A+B)^T=A^T+B^T and (AB)^T=(B^T)(A^T), yes?
 

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