Solve the Problem $r ^ { 2 } = 3600 \cos 2 \theta$

Multiple Choice

Solve the problem.
-Suppose that a radio transmission pattern can be modeled by $r ^ { 2 } = 3600 \cos 2 \theta$ , for $0 ^ { \circ } \leq \theta \leq 360 ^ { \circ }$ , where the units are miles. Determine how far the signal reaches to the east, assuming that east is represented by the direction of the positive $x$ -axis.

A) 3600 miles
B) 7200 miles
C) 60 miles
D) 120 miles