Question

Match the following for the parabola $y^2=4ax$:

• A. Focal distance
• B. Double ordinate
• C. Latus rectum

Answer 1

Latus rectum is a chord of a parabola perpendicular to axis of the parabola and passing through focus. It is the line $x=a$ in this case.

Double ordinate is a chord of a parabola perpendicular to axis of the parabola. Latus rectum is also a double ordinate of the parabola.

Focal distance is |a|, i.e., distance from the origin to the focus, and from the origin to the directrix. We take absolute value because distance is positive.