на промежутке [ - / frac{5 / pi }{2}; - / pi ][/tex]

2sin² (π+x) - cos (-π/2-x) = 0;

2 (-sinx) ² - cos ( - (π/2+x)) = 0;

2sin²x - cos (π/2+x) = 0;

2sin²x + sinx = 0;

2sinx (sinx + 1/2) = 0;

[sinx = 0; sinx = - 1/2.

[x=π*k; x = (-1) ^ (k+1) π/6+π*k, k∈Z.