# Differentiate #cos(x^2+1)# using first principle of derivative?

##### 2 Answers

#### Explanation:

For this problem, we need to use chain rule, as well as the fact that the derivative of

Formally,

where

We first need to work out the derivative of the bit inside the cosine, namely

Please see below.

#### Explanation:

We need to find

Let's focus on the expression whose limit we need.

We will use the following limits:

And

To evaluate the limit: