"Deductive reasoning" refers to the process of concluding that something must be true because it is a special case of a general principle that is known to be true. ... Therefore, this form of reasoning has no part in a mathematical proof.

Does math use deductive or inductive reasoning?

“Wait, induction? I thought math was deductive?” Well, yes, math is deductive and, in fact, mathematical induction is actually a deductive form of reasoning; if that doesn't make your brain hurt, it should.

Is deductive reasoning always true?

A deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion nevertheless to be false. ... A deductive argument is sound if and only if it is both valid, and all of its premises are actually true. Otherwise, a deductive argument is unsound.