#### Answer

$m\widehat {AB}=90^{\circ}$

#### Work Step by Step

The measure of a central angle equals the measure of its central arc. Thus,
$m\widehat {BC}=m\angle AOB=90^{\circ}$.

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Published by
Brooks Cole

ISBN 10:
9781285195698

ISBN 13:
978-1-28519-569-8

$m\widehat {AB}=90^{\circ}$

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