
Pi r-squared – everyone’s heard that formula, but where did the name for that constant come from?
How was it discovered?
What makes it unique in mathematics?
This highly illustrated book begins examining those questions in the introduction, chapter 3.14, noting 2 unusual facts about Pi: it’s infinite and irrational. Did you know that you can find any number sequence of any length in pi? (pg. 19)
Characters Pi-Rat the questioner and Little Horsey PiPi who loves math help readers learn about scholars in many eras and many lands worked diligently to discover Pi’s hidden digits.
In 1761, Johann Heinrich Lambert proved that Pi wasn’t a rational number, and the race was on for mathematicians to calculate as many of Pi’s decimal places as possible!
Srinivasa Ramanujan’s 1913 formula came to him in a dream, was ignored by university mathematicians, then proven correct over 70 years later, leading to even more efficient formulas. From pen and ink to calculating machines and computers, trillions of digits have been discovered!
But why do we need to know so many decimals of Pi? Testing new supercomputers and standing in for random number selections are just two reasons.
Pi-Rat and Little Horsey PiPi want us to have fun with Pi, with tricks for memorizing its digits, silly jokes, brain-twisting paradoxes, and how to cut a pizza exactly in half without cutting the crust.
The proofs behind historic examples cited and a glossary round out this very entertaining look at Pi and its never-ending digits. Check out the educator’s guide here: http://hello.helvetiq.com/en-us/bigbookofpi.
How many decimals of Pi can you recite?
**kmm
Book info: The Big Book of Pi: The Famous Number You Can Never Know / Anita Lehmann & Jean-Baptiste Aubin; illustrated by Joonas Sildre. Helvetiq, 2026. [author site https://www.anita-lehmann.com/] [publisher site https://helvetiq.com/us/the-big-book-of-pi] Review copy and cover image courtesy of the publisher, via Publisher Spotlight.









