let x=u and dv=1/cos^2 x use integrate by parts for the left integral and for the right integral u=x and v=x(sin x)/cos^2 x
but for the right integral you want to evaluate first , by sub u=cos x we can see that the integrate equal
use lopital for the limit
the limit equal zero after the we sub pi/2 so the integral equal ln(2)
here is my integral