Advanced Proofs: Steps and Lemmas - Expii

A proof is a process, where a sequence of logical, individual steps is chained together. This is why lemmas—facts used over and over again, like the Pythagorean theorem—can be so useful. It's also why alternative definitions and logical equivalences can be useful, and why working both forwards and backwards can be useful as a proof strategy (or as a goal-achieving strategy in life!).