CLEARLY: I don't want to write down all the "in-between" steps.

TRIVIAL: If I have to show you how to do this, you're in the wrong class.

OBVIOUSLY: I hope you weren't sleeping when we discussed this earlier,
           because I refuse to repeat it.

RECALL: I shouldn't have to tell you this, but for those of you who erase
        your memory tapes after every test...

WLOG (Without Loss Of Generality): I'm not about to do all the possible cases,
                               so I'll do one and let you figure out the rest.

IT CAN EASILY BE SHOWN: Even you, in your finite wisdom, should be able to prove
                        this without me holding your hand.

CHECK or CHECK FOR YOURSELF: This is the boring part of the proof, so you can
                             do it on your own time.

SKETCH OF A PROOF:  I couldn't verify all the details, so I'll break it down
                    into the parts I couldn't prove.

HINT:   The hardest of several possible ways to do a proof.

BRUTE FORCE (AND IGNORANCE): Four special cases, three counting arguments,
                             two long inductions, "and a partridge in a pair tree."

SOFT PROOF:  One third less filling (of the page) than your regular proof,
             but it requires two extra years of course work just to
             understand the terms.

ELEGANT PROOF:  Requires no previous knowledge of the subject matter and is
                less than ten lines long.

SIMILARLY:  At least one line of the proof of this case is the same as before.

CANONICAL FORM: 4 out of 5 mathematicians surveyed recommended this as the
                final form for their students who choose to finish.

TFAE (The Following Are Equivalent): If I say this it means that,
  and if I say that it means the other thing, and if I say the other thing...

BY A PREVIOUS THEOREM: I don't remember how it goes (come to think of it I'm 
                       not really sure we did this at all), but if I stated
                       it right (or at all), then the rest of this follows.

TWO LINE PROOF: I'll leave out everything but the conclusion, you can't
                question 'em if you can't see 'em.

BRIEFLY:  I'm running out of time, so I'll just write and talk faster.

LET'S TALK THROUGH IT: I don't want to write it on the board lest I make a mistake.

PROCEED FORMALLY: Manipulate symbols by the rules without any hint of their
                  true meaning (popular in pure math courses).

QUANTIFY: I can't find anything wrong with your proof except that it won't
          work if x is a moon of Jupiter (Popular in applied math courses).

PROOF OMITTED:  Trust me, It's true.