(sin/cos*cos)^2 * (cos/sin*sin)^2=sin^2*cos^2=(1-cos^2)*cos^2=cos^2-cos^4
(sina/cosa *cosa)^2(cosa/sina*sina)^2=(sinacosa)^2=1/4(2sinacosa)^2=1/4(sin2a)^2=1/4sin^2 (2a)
(sin/cos*cos)^2 * (cos/sin*sin)^2=sin^2*cos^2=(1-cos^2)*cos^2=cos^2-cos^4
(sina/cosa *cosa)^2(cosa/sina*sina)^2=(sinacosa)^2=1/4(2sinacosa)^2=1/4(sin2a)^2=1/4sin^2 (2a)