$\"\"$

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The function is $\"\"$ .

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$\"\"$

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Apply derivative on each side with respect to $\"\"$ .

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$\"\"$ .

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Derivative of hyperbolic trigonometry : $\"\"$ .

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$\"\"$

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$\"\"$

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Apply second derivative on each side with respect to $\"\"$ .

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$\"\"$

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Derivative of hyperbolic trigonometry : $\"\"$ .

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$\"\"$

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Sice hyperbolic identity : $\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Substitute $\"\"$ in the above equation

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$\"\"$

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Hence $\"\"$ .

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$\"\"$

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$\"\"$ .