why the value of pie is used for calculating area and perimeter of a circle?

Question

we all know that for calculating area or perimeter of a circle, we should use pie. how the value of pie is determined and what is its importance

Answer 1

Its just a ratio between a perfect circle's diameter and its circumference which is also a ratio for its radius squared and its area.
You can read all about it at wikipedia but I bet you will lose interest halfway through if not sooner.
Determined by somebody in pretty much all ancient cultures, useful for architechture mostly.
Just think if it didn't exist how you would figure it out? You dont want to have to always physically measure a circle with string or something...so you take a bunch of previous measurements and say...heh, the diameter and the circumference seem to have a constant ratio...le voila!

Do you have a math paper to write or something and you dont know how you use a search engine or wikipedia?
http://en.wikipedia.org/wiki/Pi

Answer 2

Hi Jatinpal Singh, pi is the ratio of the circumference of a circle to its diameter. It is universal constant and no one has found the absolute value. Actually it is an irrational number. But for convenience for children in lower classed pi has been equated to 22/7 and later at higher level pi is taken to be 3.14 approximately. Guinness record has been made by some as they give the value of pi with some lakh and lakh decimal places. By arc sector formula, arc length = radius of curvature x angle subtended by the arc at the centre So Cirumference / radius = angle at the centre So 2pi has been assingned for the same and hence circumference = 2 pi r. To get the area of the circle let us take a small sector which makes angle d@ at the centre. Hence the arc length will become rd@. Considering sector as a triangle its area 1/2*r*rd@ So dA = 1/2* r^2* d@ Integrating within the limits 0 to 2pi, we get 1/2*r^2(2pi-0) = pi r^2

Answer 3

Its just a ratio between a perfect circle's diameter and its circumference which is also a ratio for its radius squared and its area.
You can read all about it at wikipedia but I bet you will lose interest halfway through if not sooner.
Determined by somebody in pretty much all ancient cultures, useful for architechture mostly.
Just think if it didn't exist how you would figure it out? You dont want to have to always physically measure a circle with string or something...so you take a bunch of previous measurements and say...heh, the diameter and the circumference seem to have a constant ratio...le voila!

Do you have a math paper to write or something and you dont know how you use a search engine or wikipedia?

Answer 4

The importance of pi is in scalability. It doesn't matter whether you're looking for the area of a circle 50 meters in diameter, 100 meters in diameter or even 500 pixels in diameter. You just replace the value in the formula and you've got your answer.

Answer 5

1.draw a circle with a radius of 3.5 cm. using a compass.(dia = 7)
2. now construct a regular hexagon with 3.5 cm. side, on the circle.
3.you will get a cyclic hexagon.
4.now perimeter of the hexagon: 3.5 X 6 = 21 cm
shape & size of the perimeter is nearly that of the circle, but not quite.
5. if you continue constructing a regular polygon with 12 sides (obviously with side = 3.5/2 cm) shape & size this polygon is more closer to circle
6. if you continue this procedure to construct bigger polygons with smaller and smaller side, you will reach a stage, when you will have constructed a regular polygon with 22 sides.(with side of 1 cm.)
at this stage perimeter of this polygon will be equal to circumference of the circle for all practical purposes.
Thus circle of a radius 3.5 cm (7 cm dia), will have circumference of 22 cm, that is same as perimeter of a polygon with 22 sides each measuring 1 cm.
hope you got it. good luck

Answer 6

pie is a special number in nature as is e=2.7282.....
its origin is from the fact that we define our angle measuring unit - radians.... 1 radian is equal to the angle subtended by an arc for which the radius is equal to the circumference... so by this definition semicircle is pie radians and circle is 2*pie radians.. and there is some standard derivation for proving s=r(theta){for this defintion of angle}..
so circumference = 2*pie*r

Answer 7

Pi or π is one of the most important mathematical constants, approximately equal to 3.14159. It represents the ratio of any circle's circumference to its diameter in Euclidean geometry, which is the same as the ratio of a circle's area to the square of its radius.

Answer 8

pie is 3.14 and was determined by greek philisofers in togas. It is a constant number and is used in circles because of it's numeric value. pretty much, it is just because it fits in perfectly

Answer 9

For most practical purposes, a value of 3.1416 is good enough. Of course, the precision you use will depend on the precision you need.

There are MANY ways to calculate pi. Most involve calculating the sum of infinite series of fractions and stopping at the desired level of accuracy.

Answer 10

pie is the diffrence between 7/10 71/100
some arabic mathamtition invented it during the early 200's A.D.

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