Решить! а) tg2,5 * ctg2,5 + cos^2пи - sin^2 пи/8 - cos^2 пи/8 б) sin^2 3пи/7 - 2tg1 * ctg1 + cos^2 (-3пи/7) + sin^2 5пи/2

Tg2,5*ctg2,5+cos2π-sin²(π/8)-cos²(π/8)=1+1-(sin²(π/8)+cos²(π/8))=2-1=1

sin²3π/7-2tg1*ctg1+cos²(-3π/7)+sin²(5π/2)=(sin²(3π/7)+cos²(3π/7))-2*1+sin²(2π+π/2)=1-2+sin²(π/2)=-1+1=0