sector of circle

5cm is the radius. This means the circumference is 2 * 5π = 10π

6.28 is about 2π. This means the sector angle is 2π/10π * 360 = 72^o

 

Area of the sector = 5²π / 5

                              = 25π / 5

                              = 5π

                              ≈ 15.7cm², which is your answer :)