Вычислите:
1) sin 2a, cos 2a и tg2 a, если sin =1/2 и П/2<a < П
2) sin (a/2), cos(a/2) и tg(a/2), если cos a = 3/5 и 3П/2<a <2 П

1. sin(2a) = 2sin(a) * cos(a) = 2 * 1/2 * (-√3/2) = - √3/2

cos(2a) = cos²(a) - sin²(a) = (-√3/2) - (1/2)² = 3/4 - 1/4 = 2/4 = 1/2

tg(2a) = sin(2a) / cos(2a) = (-√3/2) / (1/2) = - √3

2. sin(a/2) = -√((1 - cos(a))/2) = -√((1 - 3/5)/2) = -√((2/5) / 2) = -√1/5

cos(a/2) = -√((1 + cos(a))/2) = -√((1 + 3/5)/2) = -√((8/5) / 2) = -√4/5