$\"\"$

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The differentiation formula is $\"\"$ .

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Let $\"\"$ , then $\"\"$ .

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Apply derivative on each side.

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Trigonometric identity : $\"\"$ .

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Substitute $\"\"$ .

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$\"\"$ .

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Substitute $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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Substitute $\"\"$ .

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$\"\"$ .

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$\"\"$

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$\"\"$ .