Question

прошу помочь со 2 номером

Answer 1

2cos x + cos^2 x = 0

t = cos x

t^2 + 2t = 0

D = 4 - 4*1 = 0

t = -2 / 2 = -1

t = cos x = -1

x = π + 2kπ, k ∈ Z