π (sometimes written pi) is a mathematical constant whose value is the ratio of any Euclidean plane circle’s circumference to its diameter; this is the same value as the ratio of a circle’s area to the square of its radius. It is approximately equal to 3.14159265 in the usual decimal notation. Many formulae from mathematics, science, and engineering involve π, which makes it one of the most important mathematical constants.

Definition of π from Wikipedia.

3.14159265 is the exactest number that can come up from my mind. I tried to memorize longer but it often went wrong for that we do not need to use it so accurately like that, instead we make it 3.14 mostly. I love π and it is an amazing constant number that I’ve been using since the seventh grade. And I remembered that I was trying to calculate π from trigonometric functions, which is one of those many ways to calculate it out, using a calculator in my hand deep in a Saturday night. Much passion about it, hah?

We call March 14 *Zu Chongzhi’s Day*, named after the man all Chinese are proud of. He calculated Pi precisely to the seventh digit after the dot with no electronic computer during his years which was more than 1,500 years ago. With only pens and paper, he made it that far, that great. Zu is one of the most brilliant mathematicians in the history of China, we all admire him as he accomplished what seemed almost impossible.

Excellent job as Zu did, that is a level everybody loving mathematics wants to reach, including me. I know I can’t expect much recognition when I get there now, because Pi has been calculated accurately to millions of digits after the dot. So I have to make it to my own “Pi”. Time to go, wait to see.