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I have a symmetric matrix whose diagonals are positive. I need to prove that this matrix is positive semidefinite.

The matrix is made up of a bunch of constants and I tried getting the eigenvalues using Maple and it was a mess. I also tried doing something I found online How to check if a symmetric $4\times4$ matrix is positive semi-definite?. I tried doing Robert Israel's answer and it ended up being a mess. Is there an easier way to prove positive semidefinite?

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    How large is your matrix? Perhaps you can post it here. I would venture to guess that you may be able to apply the Gershgorin Circle Theorem. This is noted in Calle's answer in the question you linked to.2012-11-28
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    Symmetric matrices with positive diagonals aren't always positive. (E.g., $\begin{bmatrix}1&2\\2&1\end{bmatrix}$.) What is your matrix?2012-11-28
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    If your matrix is not too large, see this : http://math.stackexchange.com/questions/40849/how-to-check-if-a-symmetric-4-times4-matrix-is-positive-semi-definite2012-11-28
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    @b555: That is the question user972276 links to above.2012-11-28
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    oops my bad, sry .. had read the q i linked just a few days abck and couldnt read this q fully >.<2012-11-28
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    @EuYu ah yes, the Gershgorin Circle Theorem works! I did not see that answer :-/ or else I would of used that. That theorem checks out on my matrix.2012-11-28
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    Glad I could help. I will post my comment as an answer so that this doesn't go unanswered.2012-11-28

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How large is your matrix? Perhaps you can post it here. I would venture to guess that you may be able to apply the Gershgorin Circle Theorem. This is noted in Calle's answer in the question you linked to.