Question

Решите уравнение 2Cos x/2+1=0

Answer 1

$2cos \frac{x}{2} +1=0 \\ \\ 2cos \frac{x}{2} =-1 \\ \\ cos \frac{x}{2} =- \frac{1}{2} \\ \\ \frac{x}{2} =+- \frac{2 \pi }{3} +2 \pi n, n\in Z \\ \\ x=+- \frac{4 \pi }{3} +4 \pi n, n\in Z$