int dx/(cos^2 x * (2 * tg x - 1)^(1/2)) = int d(tg x)/(2 * tg x - 1)^(1/2) = | tg x = t | =
= int dt/(2 * t - 1)^(1/2) = int (2 * t - 1)^(-1/2) dt =
= 1/2 * 1/(-1/2 + 1) * (2 * t - 1)^(-1/2 + 1) + C =
= (2 * t - 1)^(1/2) + C = | t = tg x | = (2 * tg x - 1)^(1/2) + C