$\"\"$

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The trigonometric function is $\"\"$ .

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Consider $\"\"$ .

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Rewrite the function.

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$\"\"$

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The sum formula for the cosine function: $\"\"$ .

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$\"\"$

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Divide numerator and denominator by $\"\"$ .

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$\"\"$ \ \

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$\"\"$ \ \

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$\"\"$

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Apply quotient property : $\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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$\"\"$ .