Найти sin a/2, cos a/2, tga/2 если знаем что cosa=3/4 a€ (0; П/2)

L sin a l = sqrt (1 - cos^2a)

l sin a l = sqrt (16/16 - 9/16) = sqrt (7) / 4

sin a/2 = 1/2 * sqrt (7) / 4 = sqrt (7) / 8

cos a/2 = 1/2 * 3/4 = 3/8

tg a = sin a/cos a, tg a = [sqrt (7) / 4] / 3/4 = sqrt (7) / 4 * 4/3 = sqrt (7) / 3

tg a/2 = sqrt (7) / 3 * 1/2 = sqrt (7) / 6