CPM Homework Help : CALC Problem 12-27

Multiple Choice: At the points where the limaςon r = 5 − 4 cos θ has a horizontal tangent, the following equation is true: Homework Help ✎
1. sin θ = 0
2. 5 sin θ = 4 sin 2θ
3. 5 sin θ = 2 sin 2θ
4. 5 cos θ = 2 cos 2θ
5. 5 cos θ = 4 cos 2θ

This is when dy/dθ = 0.

$y = r\sin(\theta)=(5-4\cos(\theta))\sin(\theta)$

You will need to use a double angle identity to rewrite your y = equation or your final answer.