A regular pentagon is such that its vertices lies on the circumference of a circle of radius 4.5cm.Find the length of a side of the pentagon to the nearest mm

Answer 1

The pentagon consists of 5 isosceles triangles, with vertex angle 360/5 = 72°, and two sides of length 4.5 cm. So the base of the triangle (the side of the pentagon) is

s = 2*4.5sin36° cm