Sin2x / (1 - cosx) = 2sinx
[sin2x - 2sinx + 2sinxcosx] / (1 - cosx) = 0
[2sinxcosx - 2sinx + 2sinxcosx] / (1 - cosx) = 0
[4sinxcosx - 2sinx] / (1 - cosx) = 0
sinx*(4cosx - 2) = 0,
ОДЗ: 1 - cosx ≠ 0, cosx ≠ 1, x ≠ 2πk, k∈Z
1) sinx = 0
x = πn, n∈Z
2) 4cosx - 2 = 0
cosx = 1/2
x = (+ -)arccos(1/2) + 2πk, n∈Z
x = (+ -)*(π/3) + 2πk, k∈Z