$\"\"$

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Prove that : $\"\"$ , Where $\"\"$ ,

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Consider the L.H.S :

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$\"\"$

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From the tangent and cotangent identities : $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Therefore, $\"\"$ .

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$\"\"$

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$\"\"$ is proved.

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