Euler's four-square identity - Wikipedia

Lectures on Modular Forms and Hecke Operators - Sage Wiki

File:Euler's formula.png - Wikimedia Commons

Lagrange's four-square theorem - Wikipedia

Lagrange's four-square theorem - Wikipedia

Orderable groups and semigroup compactifications

Half Angles from Euler's Formula

Triangular Numbers

Degen's Eight-square Identity

Training dragons the hard way - Programming Every Day!: Perfect Squares [LeetCode] Part 2: Solve it Mathematically

List of things named after Leonhard Euler - Wikipedia

Amazing visual explanation of Euler's Identity. Gauss said that if this identity was not immediately obvious, a person would never be a first class mathematician. I disagree, but this explanation makes it

List of Trigonometric Identities - Wikipedia, The Free Encyclopedia PDF, PDF, Trigonometric Functions

Computation, Free Full-Text

Euler spiral - Wikipedia

Imaginary unit - Wikiwand