$\"\"$

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Given that equation of a circle $\"\"$ .

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Let $\"\"$ be a point on the circle.

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$\"\"$ (Equation of a circle)

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$\"\"$ (Substitute $\"\"$ and $\"\"$ )

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$\"\"$

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$\"\"$ (Simplify)

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$\"\"$ (Taking square root on each side) $\"\"$

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The value of $\"\"$ .