Решить cos²x+3cos x=0

Question

Решить cos²x+3cos x=0

Answer 1

Cos^2 x+3cosx=0
cosx(cosx+3)=0
cosx=0
x=π/2+πk,k∈z

Answer 2

Cosx(cosx+3) = 0
1)cosx = 0 или 2)cosx+3=0
x = ∈ z;
2) cosx = -3
x= +- (π-arccos(3)) + 2πk, k∈z