Ответ:

2.4

Объяснение:

1. AC= bc* ctg(A) = 3*ctg(a)

2. ch = ac*sin(a) = 3*ctg(a)*sin(a) = 3*cos(a)

3. cos (a) = 4/5

4. ch = 3*4/5 = 12/5 = 2.4