How to Calculate the Digits of Pi (Without Computers)
by aoum, Mar 2, 2025, 1:27 AM
How to Calculate the Digits of Pi (Without Computers)
Pi (π) is one of the most famous irrational numbers, representing the ratio of a circle's circumference to its diameter. While there are many ways to calculate its digits, we can also do it purely mathematically without relying on programming. Below, we'll explore a few such methods!
1. Using the Basel Problem
The Basel Problem, solved by Leonhard Euler in the 18th century, involves summing the reciprocals of the squares of natural numbers. This sum has a surprising connection to π!
Hint:

Click here to reveal full solution
2. Using Trigonometry: The Arc Sine Formula
Another approach to calculating π involves trigonometry. By evaluating certain inverse trigonometric functions, we can derive the value of π.
Hint:

Click here to reveal full solution
3. Using the Gregory-Leibniz Series
The Gregory-Leibniz series is one of the earliest series to approximate π. While it converges slowly, it provides an interesting way to visualize π.
Hint:

Click here to reveal full solution
4. Using the Nilakantha Series
The Nilakantha series is another infinite series that converges faster than the Gregory-Leibniz series.
Hint:

Click here to reveal full solution
5. Using the Wallis Product
The Wallis product is an infinite product that provides an elegant formula for π.
Hint:

Click here to reveal full solution
Conclusion
There are many ways to calculate π without using computers, ranging from series like the Gregory-Leibniz and Nilakantha series to products like the Wallis formula. While some methods converge quickly, others take a large number of terms to give a good approximation. You can try these methods yourself and explore how each one approximates π with increasing precision.
For those looking for a quick approximation, the Nilakantha series and Wallis product are excellent choices. Happy exploring!
Pi (π) is one of the most famous irrational numbers, representing the ratio of a circle's circumference to its diameter. While there are many ways to calculate its digits, we can also do it purely mathematically without relying on programming. Below, we'll explore a few such methods!
1. Using the Basel Problem
The Basel Problem, solved by Leonhard Euler in the 18th century, involves summing the reciprocals of the squares of natural numbers. This sum has a surprising connection to π!
Hint:

Click here to reveal full solution
The sum of this infinite series equals:

Therefore, we can solve for π by rearranging this formula:

This series converges fairly quickly, and it's a fun fact that this was one of the first known formulas relating π to a series.

Therefore, we can solve for π by rearranging this formula:

This series converges fairly quickly, and it's a fun fact that this was one of the first known formulas relating π to a series.
2. Using Trigonometry: The Arc Sine Formula
Another approach to calculating π involves trigonometry. By evaluating certain inverse trigonometric functions, we can derive the value of π.
Hint:

Click here to reveal full solution
Using the identity for the inverse sine function, we find that:

Thus, we get:

This provides a nice way to think about π geometrically using the unit circle.

Thus, we get:

This provides a nice way to think about π geometrically using the unit circle.
3. Using the Gregory-Leibniz Series
The Gregory-Leibniz series is one of the earliest series to approximate π. While it converges slowly, it provides an interesting way to visualize π.
Hint:

Click here to reveal full solution
This infinite series alternates between adding and subtracting the reciprocals of odd numbers. In general, the nth term is given by:

While it converges slowly, summing the first few terms gives a rough approximation of π. For example:

With more terms, the approximation becomes more accurate.

While it converges slowly, summing the first few terms gives a rough approximation of π. For example:

With more terms, the approximation becomes more accurate.
4. Using the Nilakantha Series
The Nilakantha series is another infinite series that converges faster than the Gregory-Leibniz series.
Hint:

Click here to reveal full solution
This series is based on a pattern where the terms alternate in sign and involve the product of consecutive numbers. The more terms you add, the closer the sum gets to π.
For example:

This method provides a faster convergence to π compared to the Gregory-Leibniz series.
For example:

This method provides a faster convergence to π compared to the Gregory-Leibniz series.
5. Using the Wallis Product
The Wallis product is an infinite product that provides an elegant formula for π.
Hint:

Click here to reveal full solution
The Wallis product is an infinite product that converges to π when multiplied by 2. The first few terms of the product are:

Multiplying all these terms together gives an approximation for π. The more terms you include, the closer you get to the true value of π.

Multiplying all these terms together gives an approximation for π. The more terms you include, the closer you get to the true value of π.
Conclusion
There are many ways to calculate π without using computers, ranging from series like the Gregory-Leibniz and Nilakantha series to products like the Wallis formula. While some methods converge quickly, others take a large number of terms to give a good approximation. You can try these methods yourself and explore how each one approximates π with increasing precision.
For those looking for a quick approximation, the Nilakantha series and Wallis product are excellent choices. Happy exploring!
