If a number like Pi is infinite, how do we know each decimal that is newly calculated is valid?

846 views

Not a mathematician here at all so perhaps my question is phrased incorrectly.

Let’s say through thorough testing in reality, we can prove with certainty Pi is correct up until 5 decimal places,

3.14159

The computers that are calculating Pi to an endless degree, how do they validate new values that are calculated as correct and cannot be otherwise?

In: 434

36 Answers

Anonymous 0 Comments

It depends on the method you use to calculate it

Some methods use upper and lower bounds, and if both of the bounds have the first 100 digits in common, the actual value of pi must also have these 100 digits

A simpler example is √2. It’s also irrational, so its decimal expansion is infinite. 1.414² < 2 < 1.415², so 1.414 < √2 < 1.415. This means that 1.414… is definitely correct

For other methods you might be able to calculate the error in some way and get an upper bound on it. If the error is less than 0.00000000001, you know you have at least 10 correct digits

You are viewing 1 out of 36 answers, click here to view all answers.