# What is the derivative of #y=arccos(x )#?

##### 1 Answer

The answer is:

This identity can be proven easily by applying

1.)

2.)

3.)

We continue by using implicit differentiation, keeping in mind to use the chain rule on

4.)

Solve for

5.)

Now, substitution with our original equation yields

6.)

At first this might not look all that great, but it can be simplified if one recalls the identity

7.)

This is a good definition to memorize, along with