From Mathologer.

Good news! You really can still discover new beautiful maths without being a PhD mathematician.

Stumbled across this one while working on the magic squares video. Another curious discovery by recreational mathematician Lee Sallows. A simple and beautiful and curious fact about triangles that, it appears, was first discovered only 10 years ago. Really quite amazing that this one got overlooked, considering the millennia old history of triangles.

Wiki page dedicated to Lee Sallows
https://en.wikipedia.org/wiki/Lee_Sallows
His personal homepage
https://www.leesallows.com
The relevant subpage
http://tinyurl.com/y6tzsbjt

t-shirt: https://www.teepublic.com/t-shirt/300445-the-impossible-board-game
music: Campagna – Adventure of a Lifetime

Enjoy!

Burkard