$\"\"$

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The trigonometric function is $\"\"$ .

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Consider $\"\"$ .

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Substitute $\"\"$ in above function.

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$

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Apply even-odd identity : $\"\"$ .

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$\"\"$

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The value of trigonometric function : $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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The value is $\"\"$ .