CIRCLE BASICS - DIAMETER, RADIUS & PI

Circle is a round two dimensional shape, very often encountered in our daily lives. Examples of a circle are bracelets, ring, washers, popcan lid and dining plates.

All the basic terminology about a circle is very well explained in the image below:

 Mathematical Definition Of A Circle

Mathematically, a circle is a locus (or path) of all the points, whose distance from a fixed point remains fixed.
Many students take this definition as very  cumbersome. 

Let’s simplify the above words by taking an example of a cow  tied to a pole with a rope and moving around the pole. What do you  think the shape of the path will be? 

Now the word “locus of all the points” is cow’s  path and the path is always at a fixed distance (the length of the  rope) from a fixed point which is the central pole. Hope it will help kids to understand the mathematical definition (jargon words) of a circle.

All The Basic Terminology Used to Study About a Circle

 Center:  The fixed point at the center of the shape is called the center of the circle. In our example of cow, the central pole represent the center. 

Radius: The  fixed distance from center to path is known as the radius of the  circle. In cow example, the length of rope represent the radius. 

Diameter: The  length of a line across through the center is called the diameter. In  other words, diameter is twice as long as the radius. Or 2 times radius  length gives the length of the diameter. 

Pi: Pi is a constant number and it is the ratio of circumference of a circle to its diameter. Its value is 3.14159 (approximately)

Circumference: The  total length of the circular path is known as the circumference. For  example; if we want to fence the path of the cow then the length of the  fence will be circumference. 

Area of the circle: Plane surface enclosed inside the circumference is known as the area of the circle. For example; the grass inside the path covers the area of the circle formed by cow’s movement.