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;