This post is a quick recap on some fundamentals of calculating derivatives, useful for image processing and deep learning.

## Derivatives

### Calculating the derivative

Given x to the power of n, where n ≠ 0.

This is known as the power rule. For example:

### Derivative of a sum of functions

The derivative of a sum of functions is the sum of the derivatives:

So simply compute the derivatives one at a time then sum them individually.

### Derivative of a product of functions

The derivative of a product of functions is defined:

This is known as the product rule.

### Derivative of composed functions

For function composition the derivative is:

This is known as the chain rule.

If stuck, play with this calculator.