 # Pi Number It is a well-accepted practice to represent the number equivalent to the ratio of the circumference of a circle to its diameter with the Greek letter π. Perhaps this is the most famous mathematical letter — after all, it’s used by architects, physicists, astronomists, chemists, biologists, and many others.

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If one were to measure the circumference of a circle with a rope, it would turn out that it’s equal to approximately three times its own diameter — people determined this as far back as ancient times. The amazing thing is that this ratio is true for any circle, no matter what size it may be, from a button to a wheel. In other words, all circumferences can be expressed by a specific constant, which is known to be slightly greater than three. For hundreds of years, it plagued the minds of great thinkers since it clearly was a value of great signiﬁcance, and they had almost succeeded in calculating it, but the search dragged on for thousands of years. The rope is the same length as the circumference, but when it passes three times around the diameter of the circle, there’s still a leftover tail. Determining the length of that tail is exactly what has occupied the minds of mathematicians for many centuries

The Ancient Babylonians defined the value of π as equal to 3. This comes from the formula for the area of a circle S = l²/12 (where l i is the circumference of the circle), which was found in  the calculations of the Babylonians. This is a very rough estimate that leaves a lot of room for errors. Of course, they didn’t use the in designation π in Babylon — with this character we refer to the ratio of the circumference to its diameter.

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