Find the equation of the asymptote of the graph of $r = \cos 2 \theta \sec \theta.$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Find the equation of the asymptote of the graph of $r = \cos 2 \theta \sec \theta.$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
x = -1
Find the equation of the asymptote of the graph of $r = \cos 2 \theta \sec \theta.$
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