Evaluate ∫tanxsec2xdx\int \tan x \sec^2 x dx∫tanxsec2xdx by u-substitution.
12tan2x+C\frac{1}{2} \tan^2 x + C21tan2x+C
13tan3x+C\frac{1}{3} \tan^3 x + C31tan3x+C
sec2x+C\sec^2 x + Csec2x+C
tan2x+C\tan^2 x + Ctan2x+C