Activation Functions: Sigmoid

$\frac{3}{4}$ points $($graded$)$

Recall that there are several different possible choices of activation functions $f.$ Let's get more familiar with

them and their gradients.

What is the derivative of the sigmoid function, $(z)=\frac{1}{1+e^{-z}}?$ Please write your answer in terms of $e$ and $z$ :

$\frac{1}{1+e^{-}}$