#### Answer

60$^{\circ}$

#### Work Step by Step

$\angle$STR=90 because it is inscribed in a semicircle.
Since ST is equal to half SR (the hypotenuse of STR), then STR is a 30 60 90 triangle.
Arc ST=2$\angle$SRT
Arc ST=2(30)=60$^{\circ}$

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Published by
Brooks Cole

ISBN 10:
9781285195698

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

60$^{\circ}$

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