1) sin(x+Pi/2)=-корень(2)/2
x=(-1)^(k+1)*Pi/4 -Pi/2+Pi*k
3) x=-Pi/4+2Pi*n
4) sin 3x = 1/2
3x = (-1)^k Pi/6 +Pi*k
x = (-1)^k Pi/18 +Pi/3*k