Hi all, I've got a question about indirect proof, whether I have understood it correctly: a) Suppose I want to show A=>B, where A and B are two statements. In the method of indirect proof I assume that [tex]\neg B[/tex] (not B) is true and use the given statement A to show a contradiction. Therefore, B must be true (because either B or [tex]\neg B[/tex] is true). In short what I do: [tex]\neg B[/tex] true (assumption) and A true (given statement) => contradiction Is that correct? b) Now another question: Suppose I assume B is true (instead of [tex]\neg B[/tex] true) and use the given statement A such that it leads to a true statement like 1=1. Have I showed anything with that? In short what I do here: B true (assumption) and A true (given statement) => no contradiction. But that doesn't tell me anything, right?