Buffon's Needle: π from the Floorboards
Needles fall onto floorboards and reveal π. The proof without integrals goes via pieces and a noodle to a circle that always crosses the joints exactly twice.
From Erdős's BOOKTry itVisuApps
From Erdős's BOOK Learn interactively.
Elegant proofs of the kind Paul Erdős imagined in God’s BOOK
3 VisuApps
See the appsApps
All apps. Free in your browser.
Art Gallery Guards: Why n/3 Suffice
A museum floor plan falls apart into triangles, the corners get three colours, and guards on the rarest colour see everything. This makes Fisk’s proof visible that ⌊n/3⌋ guards always suffice. In free mode you drag corners, place guards yourself and see exactly what nobody sees yet.
From Erdős's BOOKTry it
Zagier's Windmills: Primes as Sums of Two Squares
Why is every prime 4k + 1 a sum of two squares? Zagier’s one-sentence proof as windmills: flipping pairs them, only one stays alone, so their number is odd – and the remaining mirror windmill splits into p = x² + (2y)². With counterexamples 7, 11, 21 and 45.
From Erdős's BOOKTry itNew ideas for your teaching.
Want to use these apps in your courses? Let’s find out what works for you.
Tell us what this is about
One form, three matters. We answer personally.
We show heyprof on your own material. Tell us what you teach and we will prepare the conversation around it.