Lagrange's theorem
# Lagrange's theorem

In mathematics, Lagrange's theorem usually refers to any of the following theorems, attributed to Joseph Louis Lagrange:

* Lagrange's theorem (group theory)
* Lagrange's theorem (number theory)
* Lagrange's four-square theorem, which states that every positive integer can be expressed as the sum of four squares of integers
* Mean value theorem in calculus
* The Lagrange inversion theorem
* The Lagrange reversion theorem
* The method of Lagrangian multipliers for mathematical optimization
