Thursday, July 15, 2010

Area of a circle


Hi Friends,

In our previous blog we learned about "An arc of a Circle". Now let us learn about " Area Of A Circle".

A circle is a simple shape of Euclidean geometry consisting of those points in planes which are equidistant from a given point called the center. The common distance of the points of a circle from its center is called its radius. Circles are simple closed curves which divide the plane into two regions, an interior and an exterior.

Example


The diameter of a circle is 8 centimeters. What is the area?

According to the question, diameter = 8 centimeters so, radius = diameter/2

radius = 8/2 centimeters


radius = 4 centimeters


A = x r2

Now put the value of radius = 4 centimeters and ╥= 3.14

Area = 3.14 x (4 cm) x (4 cm)

Therefore, area = 50.24 cm2


By cutting a circle into slices and rearranging those slices to form a rectangle, we can find the area of the circle by finding the area of the rectangle.

Example 1 divides the circle into 8 slices. Move the slices to fit them to the rectangle. They will snap into place. But 8 slices does not give us a very good rectangle. Try example 2, which divides the circle into 12 slices.

The more slices we have, the better the rectangle will be. Try using 24 slices in example 3. Compare the area of the rectangle to the area of the circle. The radius of the circle is equal to the height of the rectangle. The width of the rectangle is equal to 1/2 of the circumference or πr.


Keep reading and leave your comments.

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