cos2x - cosx = 0cos^2 x - sin^2 x - cosx = 0cos^2 x - (1 - sin^2 x) - cosx = 02cos^2 x-1 - cosx = 0cosx*(2cos x - 1)= 1cos x = 1x= 2*пи*n
cos2x - cosx = 0
cos^2 x - sin^2 x - cosx = 0
cos^2 x - (1 - sin^2 x) - cosx = 0
2cos^2 x-1 - cosx = 0
cosx*(2cos x - 1)= 1
cos x = 1
x= 2*пи*n