The focal chord that is perpendicular to the axis of a parabola is called the laths rectum.

Question:

The focal chord that is perpendicular to the axis of a parabola is called the laths rectum. For the parabola y2 = 4px in Figure 11, let F be the focus, R be any point on the parabola to the left of the latus rectum, and G be the intersection of the latus rectum with the line through R parallel to the axis. Find |FR| + |RG| and note that it is a constant.