\"\"

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In the figure, \"\" and \"\" are tangents to circle \"\".

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If a line drawn tangent to a circle and it is perpendicular to a radius its angle is \"\".

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The sum of angles of a quadrilateral is \"\".

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Here the angle are \"\" and \"\".

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\"\"

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Thus, the value \"\" is \"\".

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\"\"

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The value \"\" is \"\".