Antiderivative of sech

Theorem: The following formula holds: $$\displaystyle\int \mathrm{sech}(z)dz=\arctan(\sinh(z)),$$ where $\mathrm{sech}$ denotes the hyperbolic secant, $\arctan$ denotes the inverse tangent, and $\sinh$ denotes the hyperbolic sine.

Proof: █