Question

Решите срочно надо 2cos^2x+cos2x=0

Answer 1

2cos^2x+(cos^2x-sin^2x)=0
2cos^2x +cos^2x-(1-cos^2x)=0
4cos^2x-1=0
(2cosx-1)(2cosx+1)=0
2cosx-1=0 или 2cosx+1=0
cosx=1/2. cosx=-1/2
x=arccos(1/2) +2Пk=П/3 +2Пk. и
x=arccos(-1/2)+2Пn= -П/3+ + 2Пn, k и n -целые