Proof by Burst of Outrage:
"YOU DON'T THINK IT'S TRUE?!! WELL SHOW ME A COUNTEREXAMPLE, WHY DON'T YOU?!!"
Proof by Relentless Insistance:
"It's true! I swear it's true! It is, it is, it is!!!!"
Proof by Non Sequitar:
"And so, we derive that x is equal to 7. My uncle got hit by a truck yesterday. He was put up for a week. We had feed him his meals through a straw. Anyway, QED."
Proof by Ad Hominum:
"And so, we derive that x squared is divisible by four. By the way, you're a moron who's got the brains of a pea and [expletives deleted]."
Proof by Superior Education:
"I went to Harvard. I'm right."
ALSO
"I'm a teacher and I say so. You want to contradict me? That's three days detention for you, young man/woman!"
Proof by Circumloqution:
"And so, because A implies B, but B implies A only on the condition that C implies A, which also implies D when B implies C on alternate Sundays, I should get more credit on this homework problem."
Proof by Boredom:
And while x determines the prime factors of y, we cannot allow ourselves to be confused by the fact that z is not a factor of either x or y, and so therefore
...
...
(8 pages later)
And so, since you're probably asleep by now, I derive that x = y.