1. 2sinacosa*cos2a = 2. (1-cos2a) * tg (П/2-a) = 3. 4sinacosa/sin^2a-cos^2a = 4. 1+cos2a/sin (a-П/2) =

Найдем корни.

1) 2 * sin a * cos a * cos (2 * a) = sin (2 * a) * cos (2 * a) = ½ * sin (2 * 2 * a) = ½ * sin (4 * a);

2) (1 - cos (2 * a)) * tg (П/2 - a) = (sin^2 a + cos^2 a - cos^2 a + sin^2 a) * ctg a = 2 * sin^2 a * ctg a = 2 * sin^2 a * cos a/sin a = 2 * sin a * cos a = sin (2 * a);

3) 4 * sin a * cos a / (sin^2 a - cos^2 a) = 2 * sin (2 * a) / (sin a + cos a).

4) (1 + cos (2 * a)) / sin (a - П/2) = (sin^2 a + cos^2 a + cos^2 a - sin^2 a) / (-sin (п/2 - a)) = 2 * cos^2 a / (-cos a) = - cos^2 a/cos a = - cos a.