The chord ST of a circle is equal to the radius r of the circle. Find the length of arc ST

A.

\(\frac{\pi r}{3}\)

B.

\(\frac{\pi r}{2}\)

C.

\(\frac{\pi r}{12}\)

D.

\(\frac{\pi r}{6}\)

Correct answer is A

\(\frac{ \frac{r}{2}}{r}\) Sin \(\theta\) = \(\frac{1}{2}\) 

\(\theta\) = sin\(^{-1}\) (\(\frac{1}{2}\)) = 30\(^o\) = 60\(^o\) 

Length of arc (minor)

ST = \(\frac{\theta}{360}\) x 2\(\pi r\) 

\(\frac{60}{360} \times 2 \pi \times r = \frac{\pi}{3}\)