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Find $\"\"$ .

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The function $\"\"$ .

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The point $\"\"$ is on the circle $\"\"$ .

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Compare the equation with $\"\"$ .

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Radius of the circle $\"\"$ .

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Substitute $\"\"$ and $\"\"$ in the above equation.

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$\"\"$

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$\"\"$

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Since the point lies on third quadrant, the value of $\"\"$ .

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The point $\"\"$ is on a circle of radius $\"\"$ .

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From the figure, angle $\"\"$ lies in third quadrant.

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$\"\"$ .

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Double-angle identity : $\"\"$ .

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Apply the formula : $\"\"$ .

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Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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Therefore, $\"\"$ .

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$\"\"$ .