About
\[ \arctan x=\frac{1}{2i}\ln\!\left(\frac{1+ix}{1-ix}\right) \] \[ e^{ix}=\cos x + i\sin x \] \[ \int u\,dv = uv - \int v\,du \]
\[ \arctan x=\frac{1}{2i}\ln\!\left(\frac{1+ix}{1-ix}\right) \] \[ e^{ix}=\cos x + i\sin x \] \[ \int u\,dv = uv - \int v\,du \]