Evaluate
in this integral we will use the formula 1+tan2x=sec2x,
I = ∫sec2x sec4x dx
= ∫sec2x (1 + tan2x)2 dx
Now put tan x=t which means sec2xdx=dt,
I = ∫(1+t2)2 dt
= ∫(1+t4+2t2) dt
Now put the value of t, which is t=tan x in above integral-