Question

Which equation will produce the graph shown? 4-way >> NS * O r A. Y = 2 cos(39) O B. 3 cose = 2 2 O C. 12 = 9cos(29) O D. 8 = 5 3

Answer 1

Given:

The graph of a polar function is given.

$\begin{gathered} r(\theta)=a\cos k\theta \\ \text{Period of }\cos k\theta=\frac{2}{k}\pi \end{gathered}$

From the graph,

$\begin{gathered} k=2 \\ \text{Period of }\cos 2\theta=\pi \end{gathered}$

The graph of the polar equation,

$r^2=9\cos (2\theta)$

Answer: option C)