$\"\"$

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The function is $\"\"$ .

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Differentiate on each side with respect to $\"\"$ .

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$\"\"$ .

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Product rule of derivatives $\"\"$ .

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$\"\"$

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Derivative of co-tangent function: $\"\"$ .

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Derivative of cosine function: $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .