## Book review - "e: The Story of a Number"

Have you ever wondered where the number “e” comes from? While I was looking at geek books at the store, one called "e: The Story of A Number” by Eli Manor caught my eye. I bought it, read it, and really enjoyed it.

The book starts with the discovery of the logarithm by John Napier as a tool to calculate complex multiplications. I learned that Napier spent 20 years of his life doing extremely tedious work: compiling log tables so that computations could be done much easier. 20 years! His logs were a huge revolution in math in the 1500s, now considered to be one of the most important mathematical discoveries ever. As the book progresses, the relationship of the log function to the number e is revealed, along with many insightful discussions about other areas of math.

We often take for granted the math concepts we use without really asking ourselves where they come from. For example, when I learned how to take the derivative of a polynomial, I never bothered to learn why we were “bringing down” then decreasing the exponent. I've used the formula “exp(ix) = cos(x) + i sin(x)” many times, but I never really understood why the formula was true. Why is the derivative of exp{x} = exp{x}? While reading this book, I said to myself many times “So that's where that comes from!”

The book is very inexpensive and definitely worth the read. Here's a link to a preview of the book: http://goo.gl/lR2sP