How do you get the value of Pi?

what do you do to get the value of pi?

Divide the circumference of a circle by its diameter. In circles of all sizes this ratio is pi. There are formulae to calculate digits of pi. As a lad I calculated a few hundred digits this way (I also found all the primes < 1,000,000 with pencil and paper, what can I say, I was a nerd).

pi is an irrational number. It can not be expressed as a ratio of whole numbers or as a terminating or repeating series of digits. All the computers in the world calculating for eternity couldn't give you the exact value of pi.

Pi has been calculated to billions of digits but for nearly all practical work 3.1416 is close enough

The original question was - how do you get the value of pi? There are many ways, but the most efficient uses a formula invented by Machin.

Pi = 16 arctan(1/5) - 4 arctan(1/239)

If you put his formula into a computer that has trig functions it will produce pi to any accuracy you want, and do it very fast. As an example, in about 1996 I tried this on a computer and it took about 11 hours to find pi to 15000 places of decimals. I did it again a little while ago and it took well under a minute. It would have taken a 19th century person several lifetimes!

About ten years ago Kanada calculated over 6 billion decimal places of pi. At that time I wrote

' It is no longer worth recording values as Kanada and the Chudnovskys are in competition and the number of decimal places is into serious billions. The Chudnovskys have become American citizens and have an ‘official’ relationship with Columbia University.

If they are still around, ask them!

The value of pi given above is wrong. This is correct as far as it goes:
pi is 3.1415926535897932384626433832795
22/7 is 3.1428571428571428571428571428571
355/113 is 3.1415929203539823008849557522124
You will notice that this last is very close. This is a very lucky break for people who drive rockets to the moon.

Pi is always 3.14159265358979323846.. , or, just 3.14 when rounded to two decimal places, which is what is used in the classroom.

Thank you, judymoody100, for thanking me. It is wonderful when you are able to give something that is appreciated.