(Proof) of Contradiction: One proposition P is true, Assume not P is
true, then find a contradiction that shows not P is false, so P is true.
The Implication, P->Q, assume P and not Q is true, then finds a
contradiction that shows that P->Q is true or not Q->, not P is true.
Proof of Contradiction is proof that determines the truth of a
statement by assuming that it is false, then work to show how it is
false until the results of the assumption is a contradiction. (Webster
Dictionary)
Proof of Contrapositive is a proposition or theorem formed by
contradicting both the subject and predicate or both the hypothesis
and conclusion of a given proposition or theorem and interchanging
them (if not -b then not-a) is the contrapositive of (if a then b).
(Webster Dictionary)
