Two birds sit at the top of two different trees that are both 29.7 feet tall. The distance between the first bird and a bird watcher on the ground is 42.1 feet.
What is the angle measure, or angle of depression, between this bird and the bird watcher?

Question

Two birds sit at the top of two different trees that are both 29.7 feet tall. The distance between the first bird and a bird watcher on the ground is 42.1 feet. 
What is the angle measure, or angle of depression, between this bird and the bird watcher?

asnaseer · Answer

Assuming the distance of 42.1 feet between the first bird and the bird watcher on the ground means "horizontal distance", then this is the diagram for this problem:
|dw:1327706904963:dw|
You can find the angle of depression $\theta$ as follows:$$\tan(\theta)=\frac{29.7}{42.1}$$therefore:$$\theta=\tan^{-1}(\frac{29.7}{42.1})$$