Question

Решите уравнения: 2ctgx+2=0; 2cos^2 x+cosx=0

Answer 1

$1. \ 2ctgx+2=0 \ ctgx=-1 \ x= dfrac{3 pi }{4}+ pi k; k in Z \ \ 2. \ 2cos^2x+cosx=0 \ cosx(2cosx+1)=0 \ \ 1) \ cosx=0 \ x= dfrac{ pi }{2}+ pi k; k in Z \ \ 2) \ 2cosx+1=0 \ cosx=- dfrac{1}{2} \ \ x= dfrac{2 pi }{3}+2 pi k; k in Z \ \ x= dfrac{4 pi }{3}+2 pi k; k in Z$