2cos^2x-cosx-1=0 cos x = t 2t^2 - t - 1 = 0 D = 1 + 8 = 9 t1 = (1 + 3)/4 = 4/4 = 1 t2 = (1 - 3)/4 = -2/4 = -1/2 cos x = 1 x = 2πn cos x = -1/2 x = +- 2π/3 + 2πn при n = 1 x1 = 2π x2 = -2π/3 + 2π = 4π/3 при n = 0 x3 = 2π/3 ответ x = 2πn x = +- 2π/3 + 2πn 2π; 2π/3; 4π/3
cos x = t
2t^2 - t - 1 = 0
D = 1 + 8 = 9
t1 = (1 + 3)/4 = 4/4 = 1
t2 = (1 - 3)/4 = -2/4 = -1/2
cos x = 1
x = 2πn
cos x = -1/2
x = +- 2π/3 + 2πn
при n = 1
x1 = 2π
x2 = -2π/3 + 2π = 4π/3
при n = 0
x3 = 2π/3
ответ x = 2πn
x = +- 2π/3 + 2πn
2π; 2π/3; 4π/3