You know you're a maths geek when..

You are singing the song that goes “I got love for you if you were born in the 80s” and your girlfriend (who was born in 1979) says “what, no love for me?” and you reply “actually what I said does not imply that at all, you cant just negate both sides of a proposition and expect to get a true statement, if you reverse the implication too (to get the contrapositive) then you have a true statement, ie if I don’t love you you weren’t born in the 80s.”