Derivative of Hyperbolic Tangent Function

Theorem

 * $D_z \left({\tanh z}\right) = \operatorname{sech}^2 z$

where $\tanh$ is the hyperbolic tangent and $\operatorname{sech}$ is the hyperbolic secant.

Also see

 * Derivative of Hyperbolic Sine Function
 * Derivative of Hyperbolic Cosine Function