$\"\"$

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The angle is given by the circle A, $\"\"$

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$\"\"$

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one way to find $\"\"$ by using $\"\"$ .

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$\"\"$

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$\"\"$ is the semicircle.

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semicircle is an arc that measures $\"\"$ .

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$\"\"$

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$\"\"$ $\"\"$ (Apply arc addition postulate)

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

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$\"\"$ (Subtract 42 from each side)

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$\"\"$ (Simplify)

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$\"\"$ (Subtract)

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$\"\"$

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$\"\"$

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The value of $\"\"$ .