To determine the radius of the circle using the portion shown in the picture you have to use the formula to calculate the arc length of the segment.
![s=2\pi r((\theta)/(360))](https://img.qammunity.org/2023/formulas/mathematics/high-school/vdzuqel3k06ewu3wzmqdmbfdrbmgr47zp4.png)
Where
s is the arc length
r is the radius
π is the number pi
θ is the central angle
For the portion of the circle shown in the picture, the arc length is s=15cm and the angle is θ=27º
The first step you have to write the formula in terms of r:
![s=2\pi r((\theta)/(360º))](https://img.qammunity.org/2023/formulas/mathematics/college/57nevcxad83evv5ibbgiyib82wyotxn9xj.png)
-Divide both sides by 2π
![\begin{gathered} (s)/(2\pi)=(2\pi)/(2\pi)r((\theta)/(360)) \\ (s)/(2\pi)=r((\theta)/(360)) \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/7i47i4eohedrsagkgjyxmb9lnouhwqutas.png)
-Multiply both sides of the expression by the reciprocal fraction of (θ/360), which is (360/θ)
![(s)/(2\pi)\cdot(360)/(\theta)=r](https://img.qammunity.org/2023/formulas/mathematics/college/om4v3vsdwcvf96vrr36s7f26mfnb2jwf3p.png)
Next, replace the formula with the given arc length and angle and calculate the radius:
![\begin{gathered} r=(s)/(2\pi)\cdot(360)/(\theta) \\ r=(15)/(2pi)\cdot(360)/(27) \\ r=31.8\operatorname{cm} \end{gathered}]()
The radius has a measure of 31.8cm