y= (cosx)/(sin^2 x) * tg x(π/2-x)

cosx*((sinx/cosx) - cosx) = -sin^2(x)sinx - cos^2(x) + sin^2(x) = 0sinx - 1 + sin^2(x) + sin^2(x)) = 02sin^2(x) + sinx - 1 = 0замена: sinx = t ∈[-1;1]2t^2 + t - 1 = 0, D = 1 + 8 = 9t1 = (-1-3)/4 = -4/4 = -1t2 = (-1+3)/4 = 2/4 = 1/21) sinx = -1,x = -π/2 + 2πk, k∈Z2) sinx = 1/2x = π/6 + 2πk, k∈Zx = 5π/6 + 2πk, k∈Z