What is the Integral of tan2(x)sec(x)?

1 Answer
Feb 3, 2017

12sec(x)tan(x)12ln(|sec(x)+tan(x)|)+C

Explanation:

I=tan2(x)sec(x)dx

Let tan2(x)=sec2(x)1 which comes from the Pythagorean identity:

I=(sec2(x)1)sec(x)dx=sec3(x)dxsec(x)dx

The integral of sec(x) is well known:

I=sec3(x)dxln(|sec(x)+tan(x)|)

The integral of sec3(x) can be found through integration by parts with u=sec(x) and dv=sec2(x)dx at this link. You can also see how to integrate sec(x) there.

I=(12sec(x)tan(x)+12ln(|sec(x)+tan(x)|))ln(|sec(x)+tan(x)|)

I=12sec(x)tan(x)12ln(|sec(x)+tan(x)|)+C