Dot Product with Self is Zero iff Zero Vector/Proof 2

Proof
Let $\mathbf u \cdot \mathbf u = 0$.

Then:

The only way for this to happen is if:
 * $\norm {\mathbf u} = 0$

which implies:
 * $\mathbf u = \mathbf 0$

Now suppose $\mathbf u = \mathbf 0$.

Then: