The diameter of a circle is a line which joins two points on the circle and also passes through the centre of the circle. (In the adjoining figure (Fig 11.12) AB is a diameter of the circle; C is its centre.) Express the diameter of the circle (d) in terms of its radius (r).

Explanation

We know that diameter is twice the length of the radius of the circle.
Given that C is the centre of
a circle, CP is the radius denoted by r and AB is a
diameter denoted by dSo, Diameter =` 2 xx` Radius
=` 2 xx r`= 2r
Therefore, 2r is the diameter of the circle in terms of its radius