2sin²x+5sinx-3=0
Замена sinx = у
2y²+5y-3=0
D = 25 + 24 = 49
x₁ = (-5 -7):4 = -3
x₂ = (-5 + 7):4 = 0.5
sinx = -3 не является решением, т.к. Е(sin x) = [-1,+1]
sinx = 0.5
x = (-1)^k ·π/6 + πk
[-2π;3π] или [-12π/6;18π/6]
k = -2, x = π/6 - 2π = -11π/6
k = -1, x = -π/6 - π = -7π/6
k = 0, x = π/6
k = 1, x = -π/6 + π = 5π/6
k = 2, x = π/6 + 2π = 13π/6
k = 3, x = -π/6 + 3π = 17π/6
ответ: х = -11π/6, -7π/6, π/6, 5π/6, 13π/6, 17π/6
