Answer:
they are alternate interior angles to parallel lines.
Explanation:
The reason for this is that they are alternate interior angles to parallel lines. The straight dotted lines that represent the line of sight of each individual are parallel to each other while the elevation line in this scenario would be considered the Transversal as it passes through both of them. This ultimately causes the angles between the transversal and the line of sight to be alternate interior angles which are equal to one another, as can be seen in the attached demonstration in the image below.