Sinα·cosα·tgα-1 sin²α-tgα·ctg
SinA * CosA * tgA -1 = Sin^2A - 1 = Sin^2A - Cos^2A - Sin^2A = - Cos^2A ----------------------------------------- Sin^2A - TgA * CtgA = Sin^2A - 1 = Sin^2A - Cos^2A - Sin^2A = - Cos^2A