In a circle of diameter 40cm,the length of a chord is 20cm.Find the length of the minor arc of the chord. Answer: 20π/3?

The circle will have radius, r = 20

1. We know that it forms an equilateral triangle with sides = 20cm because we are given that the length of the chord is 20cm and the r = 20cm
2. Arc Length = r * angle, where in this case the angle is 60 degrees or π/3

How did I get 60 degrees??
1. In an equilateral triangle, by definition, the angle is 60 degrees.

Diameter = 40 cm Hence radius = 20 cm
We now have an equilateral triangle inside the circle based on the centre .
The angles of an equilateral triangle are 60 degrees ( pi/3 radians).

Circumference of a circle is C = 2pir
Arc length is A = (angle / 360 )2 pi r
Hence
A =( (pi/3) / 2pi) 2 pi (20)
Cancel down by '2 pi'
Hence
A = (pi/3) (20)
A = 20pi /3 As required !!!!