2tgt(1-sin^2t)=2tgtcos^2t=2sintcost=sin2t
7cos^t-5+7sin^2t=7(sin^2t+cos^2t)-5=7-5=2
sin(-t)+cos(-t)tg(-t)=-sint-cost*tgt=-2sint
2tgt(1-sin^2t)=2tgtcos^2t=2sintcost=sin2t
7cos^t-5+7sin^2t=7(sin^2t+cos^2t)-5=7-5=2
sin(-t)+cos(-t)tg(-t)=-sint-cost*tgt=-2sint