What is the expansion of the trigonometric expression cos(A-B)?
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cos A cos B + sin A sin B
This formula is a fundamental angle difference identity used to calculate the cosine of the distance between two angles. A helpful mnemonic is that cosine is 'contrary,' meaning the minus sign in the original expression (A-B) always flips to a plus sign in the final expansion.
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- According to the angle difference identity, what does cos(A-B) expand to?