# Chapter 8 - Section 8.5 - More Area Relationships in the Circle - Exercises - Page 379: 25

4.5 cm

#### Work Step by Step

Given that the exact area of the sector determined by 40$^{\circ}$ arc is $\frac{9}{4}\pi cm^{2}$ We need to find the length of the radius of the circle In circle of radius length r, the area A of a sector whose arc has degree m is A = $\frac{m}{360} \pi r^{2}$ $\frac{9}{4}\pi$ = $\frac{40}{360} \pi r^{2}$ $r^{2}$ = $\frac{81}{4}$ r = $\sqrt \frac{81}{4}$ r = $\frac{9}{2}$ = 4.5 cm The radius of the circle = 4.5 cm

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.