Просто по определениям надо :
1) Cosx = a/b
Sinx =c/b
tgy = a/c
2) tgB = AC/AB
SinC = AB/BC
CosC = AC/BC
3) tgx = 4/3
Cosy = 4/5 = 0,8
Siony = 3/5 = 0,6
4) Sinα = 7/29
Сosα = 21/29
tgα = 7/21 = 1/3
