10)
Given data:
The given height of the tree branch is h=15.4 ft.
The length of the ladder is l=18 ft.
The expression for the angle made by the ladder with horizontal is,

Thus, the angle made by the ladder with horizontal is 58.82 degrees.
11)
Given data:
The given triangle.
The tanB is,

The tanB is,

Thus, the value of tanB is 0.458.