2 упростите выражение: а) (sin a/1+cos a - sin a/1-cos a) • 1/2 tg (-a)​

sin(a) / (1 + cos(a)) - sin(a) / (1 - cos(a)) = (sin(a) (1 - cos(a)) - sin(a) (1 + cos(a))) / (1 - cos(a)) (1 + cos(a)) = (2 sin(a)) / (2 cos(a)) = tan(a)