Chapter 10 - Parametric Equations and Polar Coordinates - 10.6 Conic Sections in Polar Coordinates - 10.6 Exercise - Page 728: 7

$r= \frac{6}{1 + sin (θ)}$

$r= \frac{ed}{1 + e sin (θ)}$ (sine since directrix is vertical line) e = 1 since it is a parabola, vertedx is at (3, $\pi /2 $) $r= \frac{d}{1 + sin (θ)}$ Substitute (3, $\pi /2 $) into the equation $3= \frac{d}{1 + sin (\pi /2) }$ $3= \frac{d}{2}$ Thus d=6 $r= \frac{6}{1 + sin (θ)}$