Where was pi invented?

Answer 1

The number pi, as a concept, was arguably never invented, but discovered. It represents a unchanging property of every circle ever created. Nonetheless, a bit of history might shed light on the question:

The ratio of circular circumference to diameter has been a point of interest for all of recorded history, so traces of knowledge concerning pi are found all around the world. The first known guess at the ratio is by the Babylonians, who simply multiplied the diameter by three. This extremely crude estimate has been used by "street mathematicians" ever since, and may have even been used long before.

In their architectural designs, the Egyptians used two different formulas for measuring area and circumference of circles: A = (8d / 9)2 and c = 22d / 7. While reasonably accurate, the value 22/7 was the result of trial and error rather than formal calculations. As such, scholars disagree on whether to consider this as the first valid estimate of pi.

The first theoretical treatise on pi was written by Archimedes of Syracuse, Greece. He proved that the ratio is between 223/71 and 22/7, and also invented the "method of exhaustion", which can be used to estimate pi to any desired degree of accuracy by hand, although with slow results.

Perhaps surprisingly, though, the first use of the Greek letter "pi" (π) to represent this value was in a 1706 math textbook by Welsh mathematician William Jones, in which the letter was an abbreviation for "perimiter" (περιμετρος). One could argue, then, that "pi" in its modern usage was in fact invented in Wales.