Let $\text{trace}(AM)\ge0$ where $M$ is positive semidefinite, so we know that $\text{trace}(M)\ge0$ since the trace of a matrix is the sum of its eigenvalues.
Is $\text{trace}(A)\ge0$?
Let $\text{trace}(AM)\ge0$ where $M$ is positive semidefinite, so we know that $\text{trace}(M)\ge0$ since the trace of a matrix is the sum of its eigenvalues.
Is $\text{trace}(A)\ge0$?
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It's sufficient to consider diagonal matrices to see that $\text{trace}(A)$ can be anything.
Take for example $M=\text{diag}(1000,1,1)$ and $A=\text{diag}(1,-2,-3)$.