# Pi (π)

Pi has a special significance in the world of Mathematics. Pi is defined as the ratio of a circle's circumference to its diameter. That is, you can find pi by dividing a circle's circumference by its diameter. This can be done with any circle, no matter how small or large.

π = ^{C}⁄_{D}

Since pi is an irrational number, its decimal expansion never ends or repeats. It has an infinite number of digits. Here are the first 20 digits of pi:

π = 3.1415926535897932384...

To see the first 1,000 digits of pi, click here.

Pi has been known since the time of the Ancient Egyptian civilization. Mathematicians have been trying to calculate pi with more precision for thousands of years. The earliest evidence we have found shows that Egyptian mathematicians calculated pi to be 256/81, which is about 3.160. Later approximations by mathematicians produced more precise results. However, the best approximations of pi came much later thanks to the development of better techniques for working with numbers. These techniques allowed mathematicians to calculate pi to more decimal places than ever before. Now, thanks to the power of computers, we can calculate pi with extreme precision. People have used desktop computers to calculate millions, billions, and even trillions of digits of pi.

Pi appears in many formulas used in mathematics, science, and engineering. It is used in calculus, geometry, trigonometry, probability, and even physics. Whenever you need to use pi in an equation or problem, you can safely use 3.14. If you want to use a more precise value, you can use 3.1416. It's unlikely anyone will need more precision in a real-world situation.