A Cross-Section of a Parabolic Reflector Is Shown in the Figure

Multiple Choice

A cross-section of a parabolic reflector is shown in the figure. The bulb is located at the focus and the opening at the focus is $18 \mathrm {~cm}$ . Find an equation of the parabola. Let $V$ be the origin. Find the diameter of the opening $| C D | , 19 \mathrm {~cm}$ from the vertex.

A) $| C D | = 6 \sqrt { 38 }$
B) $| C D | = 18$
C) The equation is $y = 18 x ^ { 2 }$
D) $| C D | = 4 \sqrt { 414 }$
E) The equation is $y ^ { 2 } = 18 x$
F) The equation is $y ^ { 2 } - \frac { x ^ { 2 } } { 18 } = 1$