#### Answer

$m\widehat {ACB}=270^{\circ}$

#### Work Step by Step

The measure of the whole arc of a circle equals $360^{\circ}$.
Subtract out the known arc...
$360-m\widehat {BC}=m\widehat {ACB}$
$360-90=270$
$m\widehat {ACB}=270^{\circ}$

Published by
Brooks Cole

ISBN 10:
9781285195698

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

$m\widehat {ACB}=270^{\circ}$

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