Is $\mbox{tr}(A^2)$ always nonnegative?

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Does $\mbox{tr}(A^2) \geq 0$ hold for any real matrix $A$?

I think this is true but I am unable to prove this. Any further help is appreciated.

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Let $A=\left[\begin{matrix}0 & -1\\2 & 0\end{matrix}\right]$. Square it and see what happens...