Contraposition of "P if and only if Q" I'm understanding the basic idea of contraposition, when it comes to propositional logic and writing proofs, but I'm having trouble figuring out what the contraposition of "P if and only if Q" would be. It seems simple enough that the contraposition of "If P then Q" would be "If not Q then not P", but that seems too simple to be the case with if and only if. Anyone able to help?

$P \Leftrightarrow Q$ is the same as $P \Rightarrow Q$ and $Q \Rightarrow P$. So contrapose those two and you get $Not(Q) \Rightarrow Not(P)$ and $Not(P) \Rightarrow Not(Q)$, otherwise written as $Not(P) \Leftrightarrow Not(Q)$