1. tg^2 x - 4 tg x + 3 = 0;
tgx = 1; x = pi/4 + pi*k; k-Z
tg x = - 3; x = - arctg 3 + pi*k; k-Z.
2. 3 sin^2 x - 4 sinx*cos x +cos^x = 0; /cos^2 x ≠ 0;
3 tg^x - 4 tg x + 1 = 0;
tg x = 1; x = pi/4 + pi*k; k-Z.
tgx = 1/3; x = arctg (1/3) + pi*k; k-Z.
3. cos(2x) = 2 sin^2 x;
cos (2x) = 1 - 2 sin^2 x;
1 - 2 sin^2 x = 2 sin^2 x;
4 sin^2 x = 1;
sin^2 x = 1/4;
sin x = 1/2
sin x = - 1/2.
x= + - pi/6 + pi*k; k-Z.