Theorems Rectangle Rhombus Square (examples, solutions, worksheets, videos, games, activities)

Euler's four-square identity

Jacobi's four-square theorem

5. * In the following sequence of problems, we will

Lagrange's four-square theorem, polynomials, diophantine equations, prime numbers

Lagrange's Four-Square Theorem -- from Wolfram MathWorld

Lagrange's Four-Square Theorem Seen Using Polygons and Lines

CodeChef - Lagrange's four-square theorem, also known as Bachet's conjecture, states that every natural number can be represented as the sum of four integer squares. This theorem was proven by Joseph Louis

Sum of Squares Function -- from Wolfram MathWorld

Waring's Problem -- from Wolfram MathWorld

Euler Four-Square Identity -- from Wolfram MathWorld