$\"\"$

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The trigonometric functions are $\"\"$ and $\"\"$ .

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The angles both $\"\"$ are in quadrant II.

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Pythagorean identity : $\"\"$ .

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Find $\"\"$ by using Pythagorean identity.

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$\"\"$

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$\"\"$ (Since angle $\"\"$ is in quadrant II) $\"\"$

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Find $\"\"$ by using Pythagorean identity.

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$\"\"$

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$\"\"$ (Since angle $\"\"$ is in quadrant II) $\"\"$

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Find $\"\"$ by using difference formula.

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Difference formula of cosine function : $\"\"$ .

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Substitute the values $\"\"$ , $\"\"$ , $\"\"$ and

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$\"\"$ in difference formula.

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$\"\"$

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$\"\"$

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The exact value of $\"\"$ .