Tuesday, January 24, 2012

Find The Area Of A Circle

Most of us know the circles since our childhood and might have learned about them in elementary grades or in high school. But just a few of us acknowledge its definition. It can be defined as the path of all the points whose distance from a fixed central point remains fixed or constant.

There are numerous examples of circular objects we find in our day to day life, such as a round dinner plate, lid of a jar and an engagement ring, are some of them.

Before going deep into explaining tips to find the area of a circle, let's talk about the basic geometric terms related to this shape.

Center: First of all, students need to know about the center of a circle. It can be defined as a point inside the circle and is at the same distance from all of the points on its boundary. The fixed point in above definition is the center.

Radius: Next fundamental term related to this basic shape is the radius. Radius of a circle is always equal to that fixed distance from its center to its boundary. Radius is simply a piece of information which is very very useful to obtain diameter, circumference and the area of a circle. Most often the letter "r" is used to represent the radius.

Diameter: We can define the diameter of a circle as any straight line segment that passes through its center and having its endpoints on its boundaries. A diameter is the longest chord of the circle. Also the diameter is twice the radius, or in other words, two times the radius gives us the diameter.

Circumference: If we measure the length of whole of the circular boundary by putting a string over it (if possible), then it is called the circumference. Circumference is also known as the perimeter. Remember that the circumference is a length, for example, if we cut a ring and straighten it, then its length is the circumference of the ring.

The constant Pie or Pi: There is another very important property of circles known as pie (pi). We can define pie as the ratio of circumference to the diameter of the circle. It is a constant number whose value is calculated to be equal to 3.1416 (correct to four decimal places).

Area: The area of a circle represents the number of square units needed to cover it. Now that you have learned most of the basic terms about a circle, you can understand the tips to find its area very easily. Formula for area of a circle: There is a nice formula to find the area of a circle. This formula can use radius or diameter, depending upon what is given in the question. If the radius is given, then finding area of a circle is a piece of cake and we can calculate it by using the following formula;

Area = pi x radius squared or

Area = pi x radius x radius

In other words 3.14 (the fixed value of pi) times radius squared gives the area of any circle.

When the diameter is given, either divide it by 2 to get the radius and use the above formula or you can use the diameter itself to find the area as shown below;

Area = pi x diameter squared divide by 4

Yes, if you have used diameter in the formula, remember to divide by 4 once you have multiplied pi and diameter squared.

Finally, finding the area of a circle is very easy if students know the basic terminology of this prime two dimensional shape.