Sum of squares

• Analysis of variance
• Basel problem
• Brahmagupta–Fibonacci identity
• British flag theorem
• Descartes' theorem
• Explained sum of squares
• Fermat's theorem on sums of two squares
• Heron's formula
• Hilbert's seventeenth problem
• Integer triangle
• Jacobi's four-square theorem
• Lack-of-fit sum of squares
• Lagrange's four-square theorem
• Least squares
• Legendre's three-square theorem
• Mean squared error
• Multivariate analysis of variance
• Partition of sums of squares
• Polynomial SOS
• Pythagorean prime
• Pythagorean quadruple
• Pythagorean theorem
• Pythagorean triple
• Quadratic form (statistics)
• Rational trigonometry
• Reduced chi-squared statistic
• Residual sum of squares
• Square pyramidal number
• Squared deviations from the mean
• Sum of squares function
• Sum-of-squares optimization
• Sums of powers
• Total sum of squares
• cuboid
• parallelogram law
• proofs of Fermat's theorem on sums of two squares
• statistics
• sum of two squares theorem