Question 4
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 AB is a diameter of the circle; C is its centre). Express the diameter of the circle (d) in terms of its radius (r).
In the given figure, AB is the diameter and CP is the radius.
AB = AC + CB
AC= CB =CP [Radii of the same circle]
⇒AB = CP+CP
⇒AB = 2CP
Given, diameter AB= d and radius CP = r
∴ d =2r