what is the definition of pi?
370884
The 16th letter of the Greek alphabet. \n\nMathematics. A transcendental number, approximately 3.14159, represented by the symbol, that expresses the ratio of the circumference to the diameter of a circle and appears as a constant in many mathematical expressions.
86302
Pi is the ratio of a circle's circumference to its diameter (it's the same for every circle). It's an irrational number, which means that it repeats infinitely, and so far no one has been able to find a pattern in the digits. It's also a transcendental number, which means that it is not possible to construct a polynomial function f with integer coefficients such that f(pi) = 0.\n\nBecause of all that, it's not possible to come up with all the digits of pi, at least not unless someone finds a pattern to them. The world record for most digits of pi calculated is 1,241,100,000,000, which is held by Yasumasa Kanada (or, more accurately, by his computer).\n\nThe formula that Kanada used to calculate pi is large, and kind of cumbersome for anyone but a computer to use. It is, however, very efficient, which is why he used it.\n\nThe simplest formula for calculating pi is to use the arctan series. We know that arctan (pi/4) = 1, by definition of arctan. Using the Taylor Series expansion, we find\n\narctan (t) = t - t^3/3 + t^5/5  - t^7/7 + t^9/9 - ...\n\nThat series does go on forever, but so does pi, and so you can use it to calculate pi/4, by putting in 1 for x:\n\narctan (1) = 1 - 1/3 + 1/5 - 1/7 + 1/9...\n\nThis will give you an approximation of one fourth of pi. With those first five terms, we get about 0.83492 for pi/4, which gives the value of pi as about 3.33968. The real first 6 digits of pi are 3.14159, so you can see that this method needs a lot of terms to be accurate. But it is both conceptually easy and simple to remember.\n\nIf you want to learn more, try http://www.escape.com/~paulg53/math/pi/index.html , which has some other methods for how to calculate pi. The wikipedia article on pi (http://en.wikipedia.org/wiki/Pi ) also has other formulae, including some very modern ones.
1155116
Pi (a nuber near to 3.14159...), as any other positive real number has a square root. But its value (just as the value of pi itself) is not a rational number.
51187
pi is a perimeter around a circle, it's 3.14 because if we wrote the actual number of pi it wouldn't stop
421226
Ha!  I just happen to know pi to 60 decimal places off the top of my head.  \n3.141592653589793238462643383279502884197169399375105820974944
680200
Assuming this means a circle...\n\ndefn/:\n\nc=circurmfernce\nA=area\nr=radius\nd=diameter\npi=pi (~3.1415926...)\nd=2*r\n\nC=2*pi*r=d*pi\nA=pi*(r^2)...(area is pi*r squared...pie are squared-no there not their round).\nA=pi*(d^2)/4.\n\njust plug and chug...\n\nC=10*pi.\nA=25*pi.\n\nanswer:\n\nit's that simple
359053
You don't need pi to define a circle. A circle is a locus traced out such that every point is equidistant from a single point, the centre.
482997
because the definition of pi is the ratio of a circle's circumference to its diameter, or \n\npi = circumfrance:diameter\n\nthis ratio always equals 3.14.... , it's a constant
348635
Since Pi is the ratio of a circle's circumference to its diameter, it occurs wherever periodic or trigonometric structures are studied, as well as spherical structures which occur such as contour integration, measure theory (analysis, probability and statistics), and differential geometry. It is thus also a natural way of measuring angles.
481766
By definition, pi is the ratio of the circumference of a circle to its diameter. Pi is always the same number, no matter which circle you use to compute it. \nFor the sake of usefulness people often need to approximate pi. For many purposes you can use 3.14159, which is really pretty good, but if you want a better approximation you can use a computer to get it. Here's pi to many more digits: 3.14159265358979323846.
898007
It is said that the area of a circle is Pi R square.  Pie are not square. Pie are round, cornbread are square.
110639
The mathematical constant π is a real number which is defined as the ratio of a circle's circumference (Greek περιφέρεια, periphery) to its diameter in Euclidean geometry, and which is in common use in mathematics, physics, and engineering. The name of the Greek letter π is pi (pronounced pie in English), and this spelling can be used in typographical contexts where the Greek letter is not available. π is also known as Archimedes's constant (not to be confused with Archimedes's number) and Ludolph's number.
543735
A crude approximation to pi. The Babylonians had a better one 355/113 which is 3.141592
564098
I think it means quite a bit, but we haven't discovered the true meaning of it. e & pi both come up a lot in number theory & other disciplines.\n\nI think it may have to do with an oversight in our current decimal number system.
1147102
pi*(r^2)\n\nIt doesn't matter which unit you use, just make sure you're consistent.
953348
pi= the circumference of a circle divided by the diameter\n\napprox 3.14159
796855
if you mean an ellipse....\n\narea is equal to pi * minor radius * major radius