HL 5.2 - Proof by contradiction
HL 1.15: Proof by contradiction If we have tried unsuccessfully to perform a deductive proof of a statement - and cannot find a counterexample - we might next try to give a proof by contradiction (sometimes referred to as an indirect proof). In this method of proof we assume the hypothesis is true and the conclusion is false and try to arrive at a contradiction. The validity of proof by contradiction follows from the...