A proof in which you assume temporarily that the conclusion is not true, and then deduce a contradcition.
a proof in which one false assumption is made
A proof that begins by assuming the denial of what is to be proved and then deducing a contradiction from this assumption.
The method of proof that assumes the negation of what is to be proved and deduces a contradiction.
A deductive proof using contradiction or elimination to rule out all except the desired conclusion.
A proof which assumes that the desired conclusion is not true and shows that this assumption leads to a contradiction.