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

1) ctgx * tgx = 1
ctgx = -8/15
tgx = -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 = 15/17

sinx = 15/17
tgx = -15/8;
8/17;