What is int tan^3(x)*sec(x)dxtan3(x)sec(x)dx?

1 Answer
Apr 13, 2017

=(sec^3 x)/3-sec x+C=sec3x3secx+C

Explanation:

By rewriting a bit,

int tan^3 x sec x dx=int tan^2 x cdot secx tan x dx=int(sec^2 x-1)sec x tan x dxtan3xsecxdx=tan2xsecxtanxdx=(sec2x1)secxtanxdx

By substitution u=sec xu=secx, Rightarrow du = sec x tan x dxdu=secxtanxdx,

=int(u^2-1)du =u^3/3-u+C =(sec^3 x)/3-sec x+C=(u21)du=u33u+C=sec3x3secx+C

I hope that this was clear.