The angle of elevation and depression are equal because they are usually

Answer 1

measured from a horizontal line, such as the ground or a flat surface. When an object is being viewed from a certain angle, the angle of elevation is the angle above the horizontal line from the viewpoint to the object, while the angle of depression is the angle below the horizontal line from the object to the viewpoint. Since these angles are measured from the same horizontal line, they are equal in value.