# What is the equation of the tangent line of #f(x)=cotx*secx# at #x=pi/4#?

##### 1 Answer

Dec 22, 2015

#### Explanation:

First, simplify

Thus,

This is identity you should know. It can be proven through the qoutient rule

Since

We also know that

Thus, the tangent line passes through the point

Write this in point-slope form: