Given that $\cos a = \frac{1}{3}$ and $\cos b = \frac{1}{4},$ compute $\cos (a + b) \cos (a - b).$
Question:
Given that $\cos a = \frac{1}{3}$ and $\cos b = \frac{1}{4},$ compute $\cos (a + b) \cos (a - b).$
Answer:
Let's think step by step.

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-\frac{119}{144}
Given that $\cos a = \frac{1}{3}$ and $\cos b = \frac{1}{4},$ compute $\cos (a + b) \cos (a - b).$
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