In item# 1, we are only given with the height of the tree a=15 meters and we are asked to solve for the hypotenuse. Since we are not given with angle created between the rope the ground level we will assign it as ∠A = ∅
Solving for the length of the rope, we have
sin A = 15/Length of rope
Length of rope = 15 meters / sin A
In item#2, assuming that it is a right triangle we have:
8 ²= x²+3.5²
x=7.2
The smallest angle:
sin Z =3.5/8
Z = 25.95°