> f8:= x -> 2 * tan(x) * sin(x) - tan(x);

> plot(f8(x), x = 0..2*Pi, color = black);

> factor(2 * tan(x) * sin(x) - tan(x));

> plot(sin(x) - 1/2, x = 0..Pi, color = black);

> solve(sin(x) - 1/2 = 0, x);