Question

вычислите tg 2a если 1)tg a = 1/7 2)sin a = 3/5 , cos a = -4/5

Answer 1

Решение
Вычислите tg 2a если 1)tg a = 1/7
tg2a = 2tga/(1 - tg²a)
tg2a = [2*(1/7)] / (1 - 1/49) = 2/7 : 48/49 = 7/24

2)sin a = 3/5 , cos a = -4/5
tga = sina/cosa = 3/5 : (- 4/5) = - 3/4
tg2a = [2*(-3/4)] / (1 + 3/4) = - 3/2 : 7/4 = - 6/7