Area And Circumference Of Circle

Basic Terms :

Before discussing about formulas for finding area and circumference of circle , we need to study the following terms related to circle .

1. Area of circle

The area enclosed by a circle is known as area of circle.

2. Circumference of circle

The perimeter i.e, the total length of the circle is known as it's circumference.

3. Radius

A line drawn from centre of the circle to any point on it's circumference is known as it's radius.

In the above diagram, line segment OP drawn from the centre O to a point on circumference P is known as radius and is denoted by 'r'.

Similarly, you can draw OQ, OR and OS as the radii of the given circle.

4. Diameter

In the above point we discussed about radius of circle. So, we can say that diameter is equal to double the radius of circle.

Diameter is the line joining any two points on the circumference through the centre.

In the above diagram , PQ, RS, DE are the diameters of the given circle. It is interesting to note that the diameter divides the circle into two equal parts.( two semi-circles).

5. π (Pi)

This is a mathematical constant. It is defined as the ratio of a circle's circumference to its diameter. It is approximately equal to 3.14159 .

While calculating area and circumference of circle we take π= 22/7 ( this is not exact value of π) .

Formulae

Area👇. Circumference👇

πr^2. 2πr

For example-

In the above diagram the area of that circle with radius 2 cm is 12.57cm^2(area= πr^2= 22/7×2×2= 88/7=12.57cm^2) and circumference is 12.57cm ( circumference = 2.π.r = 2×22/7×2 = 88/7=12.57cm )

Note: The area and circumference of the same circle can be equal only in circles whose radius is 2

Comments

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