Stained Math # 1

\begin{widetext} \begin{gather*} \mathcal{U}(t,0) = \frac{\begin{bmatrix} \left(\cos \alpha + \sin \alpha \right) \cos \frac{\omega t}{2} & -\im \left(\cos \alpha + \expo{-\im \phi} \sin \alpha \right) \sin \frac{\omega t}{2} \\ -\im \left(\cos \alpha + \expo{\im \phi} \sin \alpha \right) \sin \frac{\omega ...