They are a fun way to demonstrate LCM and GCD too<a href="https://en.wikipedia.org/wiki/Arithmetic_billiards" rel="nofollow">https://en.wikipedia.org/wiki/Arithmetic_billiardsWith curved reflecting boundaries and parallel rays you get the beauty of catacaustics. A familiar site in a cup of coffee<a href="https://en.wikipedia.org/wiki/Caustic_(mathematics)" rel="nofollow">https://en.wikipedia.org/wiki/Caustic_(mathematics)
srean · · focus · HN ↗
<a href="https://en.wikipedia.org/wiki/Arithmetic_billiards" rel="nofollow">https://en.wikipedia.org/wiki/Arithmetic_billiards
With curved reflecting boundaries and parallel rays you get the beauty of catacaustics. A familiar site in a cup of coffee
<a href="https://en.wikipedia.org/wiki/Caustic_(mathematics)" rel="nofollow">https://en.wikipedia.org/wiki/Caustic_(mathematics)