In angle of depression, we studied that

Here, the angle of elevation of the girl to the boy is

Now, the two horizontal lines are parallel,

and line of sight is the transversal

AB and CD are parallel lines,

and BC is the transversal

∴ Angle of depression and angle of elevation are alternate angles, and they are equal

**
∴ Angle of depression = Angle of elevation
**

Thus, Angle of Depression from point A to point B is same as Angle of Elevation from point B to point A