Problem
11. Find the directrix for the polar equation \( r=\frac{8}{2-6 \sin \theta} \).
Solution
Step 1 ：1. Identify the conic form: \(r = \dfrac{8}{2 - 6 \sin \theta}\)
Step 2 ：2. Rewrite as: \(r(2 - 6 \sin \theta) = 8\)
Step 3 ：3. Calculate directrix: \(D = \dfrac{2}{6} = \dfrac{1}{3}\)
