Dave Richesonさんのイラストまとめ

The famous four color theorem says that you can color any map on the sphere with four or fewer colors. There's a similar result for every surface. For a torus, a map may require as many as seven colors, such as this one. Each of the seven "countries" borders every other country.

pencil. Here are four examples of pencil clip art. One looks correct, one is pretty good, and the other two are totally wrong.

I was just playing around with some "string art." I have recently started rewatching Game of Thrones, and so I felt the urge to make some 7-pointed stars.

As I mentioned in my previous tweet, artists often aim to have their art sit inside the 60° cone of vision. It looks like Rafael did this. By the artists' rule of thumb, this means we should not see much distortion in the painting. So, if I did my work correctly, I thought 5/8

He observed that Rafael panted some globes off to the side as perfect spheres. But, for the same reason I gave in my thread, they should be non-circular ellipses. I decided to try using what I've learned about perspective drawing to figure out what elliptical shape 2/8

I was recently reminded of Gardner's Four Bug Problem. (That's Martin Gardner, not a green thumb looking to keep pests off plants.) The problem: Four bugs sit at the corners of a 10"x10" square. Each walks directly toward its (clockwise) neighbor with the same constant 1/2

I watched some episodes of "Formula 1: Drive to Survive" on Netflix. Watching these races reminded me of the Theorem of Turning Tangents: the tangent vectors on a simple closed curve turn 360°. Intuitively, imagine a car driving counterclockwise around a Grant Prix track (you 1/4

In her @G4GCelebration talk Doris Schattschneider shared the link to the web app "[John H.] Conway's Magic Pen," which allows you to generate various tilings such as this one. She was the mathematical consultant behind it. https://t.co/yNBrgSXYWI

For a function of one variable there's a test called ``the only critical point in town.'' It says that if a differentiable function has only one critical point and it's a local max (or min), then it's a global max (min) (proof: Rolle's Theorem). However, as these images and [1/2]

Took this old NY Times 25-question language quiz. It correctly identified my home town—Rochester—where I haven't lived in 30+ years. Most distinctive answer: "What do you call the rubber-soled shoes worn in gym class or for athletic activities?" Sneakers.
https://t.co/a5vSK2bZpN