Дано sina=-15/17 Вычислитет а).cosa б).tg(3п/2-a)

cos a < 0; tg a > 0;  cos^2 a = 1 - sin^2 a = 1 - ( -15/17)^2 = 1 - 225/289 = 64/289;cos a = - 8/17; tg (3pi/2 - a) = tg a = sin a / cos a = ( - 15/17) / ( - 8/17) = 15/8;