Cos(x+п/3)cos(x-п/3)-0.25=0

Question

Cos(x+п/3)cos(x-п/3)-0.25=0

Answer 1

Cosacosb=1/2(cos(a-b)+cos(a+b))
cos(x+π/3)*cos(x-π/3)-0,25=0
1/2(cos2π/3+cos2x)=0
1/2(-1/2-1/2cos2x-0,25=0
-0,25-0,5cos2x-0,25=0
-1-0,25cos2x=0
cos2x=-4<-1<br>нет решения