Ребят, помогите)

2cos^2x+4cosx=3sin^2x

2cos^2 (x) + 4cos (x) = 3sin^2 (x) = 3-3cos^2 (x)

2cos^2 (x) + 4cos (x) = 3-3cos^2 (x)

5cos^2 (x) + 4cos (x) - 3=0

cos (x) = t

5t^2+4t-3=0

t=cos (x) = (-2+корень (19)) / 5

t=cos (x) = (-2-корень (19)) / 5 - ложный корень

x = + / - arccos ((-2+корень (19)) / 5) + 2*pi*k