Question

Решите уравнение 2cos^2x-cosx -3 = 0

Answer 1

2cos2 x-cos x -3 = 0

y=cos x

2y2-y-3=0

D=1+24=25

x1=1+5/4=3/2

x2=1-5/4=-1 

 

 cos x=-1

 х = π + 2πk;