How will I find the length of the side of the pentagon whose radius is 5cm using the Law of Sine? No angle gvn?

The question goes like this: "A regular pentagon is inscribed in a circle whose radius is 5 cm. Find the length of the side p of the pentagon by using the Law of Sines." Only two sides were given with no angles at all. How am I going to solve this using the Law of Sine?