tg x+ctg x=2 .........
Tg x+ctg x = 2 tg x+(1 / tg x) = 2 (tg^2 x+1) / tg x = 2 tg^2 x - 2tg x +1=0 (D) tg x: D = (-2)^2 -4 (1*1) = 0 tg x = (2 +- корень из 0) / 2 = 1 tg x = 1 =>x = пи / 4