Answer:
The height of the river dam is 83.9 m
Explanation:
Given : AB is the height of the river dam
∠ACB=40°
BC = 100 m
To Find: The height of river dam i.e. AB
Solution:
Refer the attached file.
Perpendicular = AB
Base = BC = 100
To find the height of the river dam we will use trigonometric ratio.





Hence the height of the river dam is 83.9 m