Hermitian Matrix has Real Eigenvalues/Proof 2

Proof
Let $\mathbf A$ be a Hermitian matrix.

Then, by definition, $\mathbf A = \mathbf A^\dagger$, where $^\dagger$ designates its Hermitian conjugate.

Let $\lambda$ be an eigenvalue of $\mathbf A$.

Let $\mathbf v$ be an eigenvector corresponding to the eigenvalue $\lambda$ of $\mathbf A$.

Denote with $\innerprod \cdot \cdot$ the inner product on $\C$.

We have that $v \ne 0$.

Hence by non-negative definiteness of an inner product:
 * $\innerprod v v \ne 0$

and we can divide both sides by $\innerprod v v$.

Thus:
 * $\lambda = \overline \lambda$

By Complex Number equals Conjugate iff Wholly Real, $\lambda$ is a real number.

$\lambda$ was arbitrary, so it follows that every eigenvalue is a real number.

Hence the result.