The Snake Lemma in unflattering detail

“Proving the snake lemma is something that should not be done in public…” ~ Paolo Aluffi. The Snake Lemma is a theorem about exact sequences of modules, and is an important tool in homological algebra. Almost every textbook that includes the Snake Lemma leaves it as an “easy” exercise. Atiyah–MacDonald is kind enough to construct … Continue reading “The Snake Lemma in unflattering detail”