Proof by contradiction was my favorite method in college.  I think it's easier because you know where to start and you just move forward.  So even to prove that things are true, I'd just assume the converse and show a contradiction.

Because a non-contradiction based proof seems harder.  You know where you want to go, but you don't know where to start.

I remember such proofs were considered less elegant or even rejected by some mathematicians in earlier times, but don't know the historic context anymore. 

Scroogey

Pulling out an inductive proof by contradiction, along with an obscure (to me) formula, is impressive for someone who doesn't do proofs on a regular basis :)


SimpleStacker

science

[Daily puzzle] is this number rational

south_korea_ln

No, I enjoyed college level math thirty-plus years ago, but was more interested in computer programming than pure math.