history, Milestones, Murderous Maths, Simon teaching, Simon's sketch book

Another evening tea

Simon was showing Dad a graph of how technology is developing exponentially, y = a^x. Dad asked for a specific value of a, and Simon said: “All exponentials are stretched out or squished versions of the same thing.” He then quickly came up with the proof (“a few lines of relatively simple algebra”). “If all exponentials are pretty much the same, that means that all exponentials have proportionately the same derivative.”

“I’m converting a to e, because e has a place in calculus that we can work with”.
Geometry Joys, Milestones, Murderous Maths, Notes on everyday life, Simon teaching, Simon's sketch book

Geometric Definition of e

The idea comes from a video by Mathologer. Simon sketches a geometric definition of the Euler’s number (e) using integrals. He messed up a little with the integral notation, but corrected it later (after we stopped filming). Please see the photos below: