## (MongoDB) How to use –fork On Windows for multiple servers

Although for most of developers, deploying database On Windows is not advised. For beginners like me, always need do some practise on Windows.

Currently I am studying replica sets, which asks me to run multiple servers at the same time with following commands.

# 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:

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