Question: do you know all the number in pi?

Edward Smart answered on 28 Mar 2025:

No I don’t! In fact, no-one does because Pi is an irrational number, which means its decimal representation goes on forever with no repeating patterns. Note, 3.33333333333… goes on forever, but we don’t regard this as irrational because we can write it as an exact fraction, 3 and 1/3.
Some good approximations for Pi include 22/7 but a really good one is 355/113, that will give you 7 correct digits of Pi.

Apparently, even for space travel, NASA uses just 15 digits of Pi because that gives them all the accuracy they need.
That said, people do like to try and compute as many digits as they can and I think at this moment, they have reached 60 trillion +, which is quite mad!

There are number of formulae for Pi. One of my favourites is to consider this infinite sum…

1 + 1/4 + 1/9 + 1/16 + 1/25 + 1/36 + …
You can see how this is constructed. It is the sum of 1 divided by all the square numbers (1 = 1^2, 4 = 2^2, 9 = 3^2 and so on).

Even though the sum is infinite, it does add up to a finite value. Which is….. (Pi^2) / 6 !!!!!
How mad is that!?!

There are a lot of interesting equations that link Pi.