In this paper it is shown that $C=\frac{n}{2}$ is the best constant for the above problem. Also the similar problem for Hermitian matrices is also investigated and it is shown that for this more larger set of matrices, the best constant $C$, is equal to $\cot(\frac{\pi}{2n})$.

In my paper it is shown that $C=\frac{n}{2}$ is the best constant for the above problem. Also the similar problem for Hermitian matrices is also investigated and it is shown that for this more larger set of matrices, the best constant $C$, is equal to $\cot(\frac{\pi}{2n})$.