Sin^2a+cos^2a+cos2a/cos^2a/2-sin^2a/2 =
Sin²α + cos²α +cos2α/(cos²α/2 -sin²α/2) =1+cos2α/cosα =(cosα + cos2α)/cosα = = 2cosα3α/2 *cosα/2 /cosα . ===================================== Sin^2a+cos^2a+cos2a/ ( cos^2a/2-sin^2a/2)=