As a mathematician it is always important to know all the tools in your proof arsenal, and therefore The 36 Methods of Mathematical Proof is an indispensable guide for anyone who does any work in the field. Some of the methods include:

**Proof by hasty generalization:**“Well, it works for 17, so it works for all reals.”**Proof by deception:**“Now everyone turn their backs…”**Proof by supplication:**“Oh please, let it be true.”**Proof by poor analogy:**“Well, it’s just like…”**Proof by avoidance:**Limit of proof by postponement as it approaches infinity**Proof by design:**If it’s not true in today’s math, invent a new system in which it is.**Proof by authority:**“Well, Don Knuth says it’s true, so it must be!”**Proof by intuition:**“I have this gut feeling.”

(via Diary of a Math Student)