Question

помогите решить cos2x-cosxcos3x=0

Answer 1

cos2x-cosx=cos3x 
cos2x = cos3x + cosx 
cos2x = 2cos2x * cosx 
cos2x(cosx - 1/2) = 0 
cos2x = 0 
2x = pi/2 + k*pi 
x = pi/4 + k*pi/2 

cosx = 1/2 
x = +-pi/3 + 2 k*pi