2a² = 2(√3 - 1)² = 2(3 - 2√3 + 1) = 6 - 4√3 + 2 = 8 - 4√3 = 4(2 - √3)
2sin^2 x/4 +√2 /2=1+cos(2* π/8) -1
sin^2 x/4 =cosπ/4-√2/2
sin^2 x/4=√2/2-√2/2
sin^2 x/4=0
sinx/4=0
x/4=πn, n-celoe
x=4πn
..........................
-90+0,7*(-10)³=-90+0,7*(-1000)=-90-700=-790
sin²α+cos²α=1; sin²α=1-0,6²=1-0,36=0,64
sinα=0,8 - это ответ. При π/2<α<π sinα>0.