A result that has been **proved to be true** (using operations and facts that were already known).

Example: The "Pythagoras Theorem" says that a^{2} + b^{2} = c^{2} for a right angled triangle. There are many proofs it is **true**.

Other examples:

• Intermediate Value Theorem

• Binomial Theorem

• Fundamental Theorem of Arithmetic

• Fundamental Theorem of Algebra

Lots more!

A Theorem is a major result, a minor result is called a Lemma.

See: Pythagoras Theorem