1. решите уравнение 2 cos x + 5 cos x - 3 cos x = 0 2. решите уравнение cos 3x + cos 2x = sin 5x

2.)Решение cos3x+cos2x=sin5x 2cos(3x + 2x)/2* cos(3x - 2x)/2 = sin5x 2cos2,5x * cos0,5x - sin2*2,5x = 0 2*cos2,5x * cos0,5x - 2*sin2,5x * cos2,5x = 0 2cos2,5x * (cos0,5x - sin2,5x) = 0 1) cos2,5x = 0 2,5x = + k, k Z x = 2/5 + 2k/5, k Z 2) cos0,5x - sin2,5x = 0 cos0,5x - cos(/2 - 2,5x) = 0 - 2sin(0,5x + 2,5x)/2 * sin(0,5x - 2,5x)/2 = 0 3) sin1,5x = 0 1,5x = n, n Z x = 2n/3, n Z 4) sinx = 0 x = m, m Z 1.)cos2x-3cosx+2=0 2cosx-1-3cosx+2=0 450-720 2cosx-3cosx+1=0 cosx=t 2t-3t+1=0 t=1cosx=1x=2n t=1/2cosx=1/2x=+-/3+2n под условие x[-4;-5/2] подходят x=-4 и x=-11/3