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

MathType on X: Lagrange's four-square theorem asserts that any positive whole number can be written as the sum of four squares of integers. Leave an example in the comments! #MathType #NumberTheory #math #

LAGRANGE'S FOUR SQUARE THEOREM Theorems, Lagrange theorem, Number theory

Chit-chat on Lagrange's four-square theorem

Seatings and Sums of Squares

数论代考, 四平方和定理The four square theorem 代写

Table 3 from Extended Lagrange's four-square theorem

Lagrange's four-square theorem - Wikiwand

Sum of two squares theorem - Wikipedia

Lagrange and the four-square theorem - Archive ouverte HAL

Sum of Squares Function -- from Wolfram MathWorld