1. sin 3x = sin x 2. 2 cos^2 x + 5 cos x + 2 = 0

Question

1. sin 3x = sin x
2. 2 cos^2 x + 5 cos x + 2 = 0

Answer 1

1) sin3x-sinx=0
sin2x=0
2x=nk
x=nk/2
2) cosx=a
2a^2+5a+2=0
D=5^2-4*2*2=25-16=9
a1=-5+3/4=-1/2=-0,5
a2=-5-3/4=-2
cosx=-0,5
x=n-arccos(-0,5)+2nk