Let $A$ be a Hermetian matrix having all district eigenvalues $\lambda_1,\lambda_2,\ldots,\lambda_n$. If $X_1, X_2,\ldots X_n$ are corresponding eigenvectors then show that the $n\times n$ matrix $C$ whose $k^{th}$ column consists of the vector $X_k$ is nonsingular.
I need to show that matrix $C$ in the question (above or image) is non singular.