Jeffery Mensah

The snake lemma is a fundamental tool of homological algebra which is primarily used in the construction of the homology long exact sequence. It's proof, like many others in homological algebra, is an exercise in diagram chasing...

The Yoneda lemma, according to Ravil Vakil in Foundations of Algebraic Geometry, is an "important exercise you should do once in your life." This fundamental result is often said to be difficult to conceptualize...

Here are two puzzles of my own invention concerning finite arithmetic progressions in cyclic (or monothetic) groups. An example this is a sequence of regularly scheduled meetings spread throughout multiple years (e.g. 10 meetings occuring once every 60 days)...