Simplify $\cos 54^\circ \cos 4^\circ - \cos 36^\circ \cos 86^\circ.$

Enter your answer is a trigonometric function evaluated at an integer, such as "sin 7".  (The system will assume that the angle is in degrees.)
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Simplify $\cos 54^\circ \cos 4^\circ - \cos 36^\circ \cos 86^\circ.$

Enter your answer is a trigonometric function evaluated at an integer, such as "sin 7".  (The system will assume that the angle is in degrees.)
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\cos 58^\circ
Simplify $\cos 54^\circ \cos 4^\circ - \cos 36^\circ \cos 86^\circ.$

Enter your answer is a trigonometric function evaluated at an integer, such as "sin 7".  (The system will assume that the angle is in degrees.)
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