Circumference of a circle

Aug 08, 2022, 16:45 IST

Introduction and use of Circle

In our daily life, we come across many circular objects like coins, cakes, plates, wheels, wheelbarrows, brooches, bangles, flower beds, etc. So, the problem of finding perimeters and area of plane circular figures has great practical importance. 

Review of Perimeter and Area of a Circle 

Circle: A circle is a closed curve consisting of a set of all those points of the plane which are at a constant distance from a fixed point in  the plane.

Centre: The fixed point is called its centre.

Radius: The constant distance is called its radius. It is the line segment joining any point on the boundary (circumference) to the centre.

Circumference of a circle

The boundary  (or perimeter) of a circle is called its circumference.

The circumference of a circle bears a constant ratio with its diameter. this constant ratio is denoted by Pi (), a Greek letter.

In other words, 

Formula of Circumference of a circle

The boundary or perimeter of a circle is called its circumference.The circumference of a circle ca be calculated by formula 2Pi r

Area of Circle:

Cut a circle of radius r into a number of sectors and rearrange them as shown in figure given in below mentioned pdf 

The sector can be rearranged together in nearly a rectangle of length   and breadth r.

Area of the circle = area of the rectangle 

Area Enclosed Between Two Concentric Circles:

The fig. bounded by two concentric circles is called annulus.

If the radii of the outer and inner circles are R and r, respectively, then

Find below Circumference of a circle formula and example