∫tan3x - xtan2x. dx
∫tan2x (tan x - x).dx
∫sec2x - 1(tan x - x).dx
∫sec2x.tan x.dx - ∫x.sec2x.dx - ∫tan x.dx + ∫x.dx
Let tanx = t then sec2x.dx = dt . the break u.v in ∫x.sec2x.dx
directly
(tan2x)/2 - xtanx + ∫tan x.dx - ∫tan x.dx + (x2)/2
(tan2x)/2 - xtanx + (x2)/2