[crop circles] * MARCH 14, WRITTEN OUT AS 3/14 IN THE US AND A FEW OTHER COUNTRIES, IS Π DAY, AS THOSE ARE THE FIRST THREE DIGITS OF THE FAMOUS NUMBER. * Π IS ONE OF THE MOST IMPORTANT AND FASCINATING NUMBERS IN MATH. ------------------------- Happy π day! March 14, when written out in the American date style of month/day, comes out as 3/14. That coincides with the three first digits of π: 3.14. π is one of the most important numbers in math. As you may recall from basic geometry, π is defined as the ratio of a circle's circumference to its diameter. So, anywhere where circles or cyclical things show up, π tends to show up as well. It would be impossible to do geometry, trigonometry, calculus, analysis of waves, or most branches of math without the concept of π. As a number, π is also itself fascinating. π is an irrational number — it can't be written as a fraction of two integers, no matter what integers you choose. One consequence of that is that the infinite decimal expansion of π never adopts a repeating pattern. π is actually a step further than an irrational number, and is what mathematicians call a transcendental number. There are plenty of irrational numbers — the square root of 2, or 3, or any prime number is irrational, as are cube roots and higher-power roots of primes. Transcendental numbers, like π, aren't the roots of any rational number. Another way of saying that is that π raised to any power is still irrational. Even though circles, and therefore π, have been a subject of study for millennia — the great Greek mathematician Archimedes came up with a clever way of approximating π by drawing polygons inside and outside a circle to estimate the circle's circumference — π was only proven to be irrational in the 18th century, and transcendental in the 19th. π day comes with a few caveats, the biggest being that most of the world doesn't write March 14 as 3/14, but instead as 14/3. Still, for residents of the countries that do, π day offers a fun chance to reflect on a very special number. SEE ALSO: IF YOU CAN SOLVE ONE OF THESE 6 MAJOR MATH PROBLEMS, YOU'LL WIN A $1 MILLION PRIZE Join the conversation about this story » NOW WATCH: What would happen if humans tried to land on Jupiter
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