# Logistic Regression with a Neural Network mindset

Welcome to your first (required) programming assignment! You will build a logistic regression classifier to recognize cats. This assignment will step you through how to do this with a Neural Network mindset, and so will also hone your intuitions about deep learning.
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## (Neural Network) Derivative of sigmoid function

$f(z)=\frac{1}{1+e^{-z}}$
$f'(z)=f(z)(1-f(z))$

Process:

$$f(z)=\frac{1}{1+e^{-z}}$$
$$f'(z)=\frac{e^{-z}}{{(1+e^{-z}})^{2}}$$
$$=\frac{1+e^{-z}-1}{{(1+e^{-z}})^{2}}$$
$$=\frac{1}{(1+e^{-z}}) – \frac{1}{{(1+e^{-z}})^{2}}$$
$$=y(1 – y)$$