CPM Homework Help : APCALC Problem 12-27

Multiple Choice: Which of the following equations can be used to determine where $r(θ) = 5 - 4\cos(θ)$ has a horizontal tangent?

Hint:

This is when $dy/dθ = 0$ .

Step:

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

More Help:

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