Lagrange's Four-Square Theorem, PDF, Number Theory

Chit-chat on Lagrange's four-square theorem

Jacobi's four-square theorem - Wikipedia

What's so interesting about squared numbers? Lagrange's Four Square Theorem

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

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

SOLVED: 8.35 (Lagrange's Four-Square Theorem) If n is a natural number, it can be expressed as the sum of four squares. A lattice in 4-space is a set of the form (x,y,z,w)

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

Lagrange's Four Squares Theorem

Pythagorean Theorem

Why was this visual proof missed for 400 years? (Fermat's two square theorem)