I have added the diagram of the question.
Answer:
∠2 is the angle of elevation from the radar tower to the airplane
Explanation:
First of all, let's define angles of elevation and depression:
angle of elevation is the angle between the horizontal line of sight and the above object you're looking at. It means that your position is lower than the that of the object
angle of depression is the angle between the horizontal line of sight and the below object you're looking at. It means that your position is higher than that of the object.
Now, in the given, it is obvious that angle 2 is formed between the horizontal line of sight of the radar tower and the plane (object) above it.
Therefore, based on the definition, angle 2 is the elevation angle of elevation from the radar tower to the airplane
Hope this helps :)
