Let $V$ be a complex inner product space. For any $u, v \in V$.
$$\lvert\langle{u},{v}\rangle\rvert^2 \leq \lVert{u}\rVert^2 \lVert{u}\rVert^2$$
$$\mathcal{X} = \left\{x_1, x_2, \cdots, x_n\right\}$$
$$\mathcal{X} = \left{x_1, x_2, \cdots, x_n\right}$$