2cos^2a-1/[2tan(45度-a)*sin^2(45度+a)]
=2cos^2a-1/[2ctg(45度+a)*sin^2(45度+a)]
=2cos^2a-1/[2cos(45度+a)*sin(45度+a)]
=2cos^2a-1/sin(90度+2a)=2cos^2a-1/cos(2a)
=2cos^2a-sec(2a)