Activity 1: Fill Me. Fill in the blanks to complete the definitions, 1. An angle of_______ is the angle formed by a horizontal line and a line of sight to a point above the line. 2. An angle of_______ is the angle formed by a horizontal line and a line of sight to a point below the line. 3. The line which is drawn from the eyes of the observer to the point being viewed on the object is known as the________. 4._________ is a straight line on the coordinate flat surface where all points on the line have the same y-coordinate. 5. If two rays or two line segments meet at a common endpoint, then the point is known as the_______.