# Power Rule, Product Rule, Quotient Rule and Chain Rule

Recently, I had a need to use derivative. So I decided to make this short overview of the four fundamental rules to refresh and recall my knowledge in evaluating derivatives.

The overview doesn’t contain any proves, it’s just a reference where you and I can quickly find differentiation rules that can be applied on derivatives. Moreover, I skipped some other rules such as sum or difference rule.

#### Power Rule

The power rule says:

For n = 0 we should apply constant rule:

#### Product Rule

Let say we want to take a derivative of a product of two functions  and.

In this case we can apply the below formula:

Here goes an example with three functions:

I think the idea is very simple so we can go ahead with the next rule.

#### Quotient Rule

The quotient rule can be applied in case if you want to take a derivative of a function that is quotient of two other functions.

So the derivative will be equal to:

By the way you can use product rule instead of quotient rule.

#### Chain Rule

The chain rule is a rule for computing derivative of the composition of two or more functions.

The formula of the chain rule can be expressed as:

For example, what is derivative of :