CLASS-6
CIRCLE-DEFINITION

CIRCLE-DEFINITION -

A circle is the collection of all those points, say P, in a plane each of which is at a constant distance from a fixed point in that plane. 

The fixed point is called the centre and the constant distance is called the radius of the circle.

The radius of a circle is always positive. The adjoining figure shows a circle with C as its centre and r as its radius. 

Note that, the centre of a circle does not lie on the circle. For convenience, a circle may be named by its centre. 

In the above figure/picture, , it is a circle C.

Let, C be the centre of the circle, and r its radius. If P is a point on the circle, then the line segment CP is a radius of the circle and its length is r.  

If Q is another point on the circle then CQ is another radius of the circle. note that all radii (plural of radius) have one point in common (is called origin), which is the centre of the circle. Also CP = CQ = r. 

Thus, it can be conclude that, All radii of a circle are equal.