a). = sin^2 b
б). = tg^2 3a
в). = sin^2 a+(sin^2 a+cos^2 a) * cos^2 a=sin^2 a +cos^2 a=1
г). = sin x*sin x-sin x+sin x-1=sin^x-sin x+sin x-1=-(1-sin^2 x)=-cos^2 x
