# The Sect of Numbers: Pythagoras’ theorem by Claudi Alsina

The Sect of Numbers: Pythagoras’ theorem is the 5th book in the series Our Mathematical World, by National Geographic. I’ve enjoyed this book a lot. Some of the books in the series might not be very entertaining, but this one was. Alsina integrated a few jokes and the mathematical formulas aren’t that extensive. If you have an interest in mathematics, I imagine you’d like the book as much as I did. In the book, the author tells stories like what happened after Pythagoras death, his followers continued their work. Theano, his wife and his daughter continued their work. It is believed Theano worked on the golden ratio. In time, Pythagoras became a sort of a mystical figure, performer of miracles, attributed with magical powers. That was a fascinating detail I wasn’t aware of.

One of the problems with the knowledge accumulated by Pythagoras and the Pythagoreans is that it was not written. Papyrus was invented, but it was not widely available.

The Sect of Numbers goes from the story of Pythagoras to the history of √2, the spiral of Theodorus, uses of Pythagoras’ theorem in paintings. This theorem is not only useful to calculate the hypotenuse of a right angle triangle if you know the sides. The Pythagorean mathematical and philosophical project made it clear that is possible to understand the world through numbers.

Hippasus, who was a Pythagorean philosophers, asked the question what would the hypotenuse of a right angled triangle with the catheti of length 1 is. The answer is √2. The legend goes that he was drowned at see as punishment for suggesting that the natural world can’t be measured only in fixed, natural numbers. The Pythagoreans found the irrational numbers to be too shocking.

## The Sect of Numbers: Pythagoras’ theorem

My rating: 4/5 Stars.
Would I recommend it: Yes