Найти sina, cosa, tga если дано :
ctga=-8/15 , п/2 < a <п

1) ctgx * tgx = 1ctgx = -8/15tgx = -15/8;2) 1 +  = 1/;1 + 225/64 = 1/;289/64 = 1/;17/8 = 1/ cosx;17cosx = 8;cosx = 8/17;3)  +  =1;64/289 +  = 1; = 1 - 64/289; = 225/289;sinx = 15/17sinx = 15/17tgx = -15/8;8/17;