$\"\"$

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The identity is $\"\"$

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Consider the right hand side of the identity: $\"\"$ .

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Definition of the hyperbolic functions:

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$\"\"$ and $\"\"$ .

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$\"\"$ and $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .