Question

спасите, помогите!!! 1-(cos^2)2x = sin3x - cos(п/2+x)

Answer 1

1-(cos^2)2x = sin3x - cos(п/2+x)

(cos^2)2x+(sin^2)2x-(cos^2)2x=3sinx-4(sin^3)x+sinx

2(sin^2)2x-4sinx+4(sin^3)x=0

 2sinx*cosx-4sinx+4(sin^3)x=0

2sinx(cosx+2(sin^2)x-2)=0

cosx-2+2(sin^2)x=0 

cosx-2(sin^2)x-2(cos^2)x+2(sin^2)x=0  

cosx-(cos^2)x=0  

 

cosx(1-2cosx)=0

1-2cosx=0

cosx=1/2, значит, x=60градусов