Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Derivatives Along a Segment for Functions on a Euclidean Open Set
lemmalem:segment-derivative-c1-2026aMultivariable CalculusLet be a natural number, let be an open subset of Euclidean space , let be the real numbers, and let be the real line. Let be of class on (via clause 3 there, being real-valued), wit…- Let be natural numbers, let be an open subset of Euclidean space , let be the real numbers, and let , with coordinate functions . For a natural number , we define what it means for …
Partial Derivative on a Euclidean Open Set
definitiondef:partial-derivative-euclidean-2026aMultivariable CalculusLet be a natural number, let be an open subset of Euclidean space , let be the real numbers with absolute value , let , let , and let . We say that the…Euclidean Points as Tuples of Real Numbers
lemmalem:euclidean-points-are-tuples-2026aSet TheoryMultivariable CalculusLet be a natural number, let be the initial segment determined by , and let be the set of real numbers. Euclidean space is introduced there as the set of all ordered -tuples with each , the term…A Convex Function is Continuous near an Interior Point
corollarycor:convex-function-continuous-near-interior-point-2026aAnalysisMultivariable CalculusLet , , , , the Euclidean norm , the Euclidean metric and the closed balls of Closed Ball in a Metric Space be as in A Convex Function is Lipschitz on a Ball around an Interior Point. Regard…A Convex Function is Lipschitz on a Ball around an Interior Point
theoremthm:convex-function-lipschitz-near-interior-point-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the initial segment determined by , and let be the set of real numbers with the operations and the order of its ordered field structure, with the absolute value written . On Euclidean space…Increment Bound for a Convex Function through an Extended Point
lemmalem:convex-function-increment-bound-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the set of real numbers with the operations and the order of its ordered field structure, let be a convex subset of Euclidean space , a real vector space by…A Convex Function Bounded Above on a Set Symmetric about a Point is Bounded Below on It
lemmalem:convex-function-bounded-below-reflection-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the set of real numbers with the operations and the order of its ordered field structure, let be a convex subset of Euclidean space , a real vector space by…A Convex Function is Bounded Above near a Point by its Values at Coordinate Neighbours
lemmalem:convex-function-bounded-above-crosspolytope-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the initial segment determined by , and let be the set of real numbers with the operations and the order of its ordered field structure, with the absolute value written . Let be a convex su…Jensen's Inequality for Finite Convex Combinations
theoremthm:jensen-inequality-finite-2026aAnalysisMultivariable CalculusLet and be natural numbers with and , let be the real numbers with the order of its ordered field structure, and let be the initial segment determined by . Let be a convex subset of Euclidean space , regarded…Properties of the Norm of a Symmetric Real Matrix
lemmalem:symmetric-matrix-norm-properties-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number with and let be the real numbers with the order of its ordered field structure and the absolute value . Let and be symmetric real matrices and let . Write for the…Small Cases, Reduction, and Membership for Convex Combinations
lemmalem:convex-combination-properties-2026aAnalysisLinear AlgebraMultivariable CalculusLet and be natural numbers with and , let be the real numbers with the order of its ordered field structure, and for a natural number let be the initial segment determined by . Regard Euclidean space as a rea…A Closed Euclidean Ball is Convex and Compact
lemmalem:closed-euclidean-ball-convex-compact-2026aAnalysisTopologyMultivariable CalculusLet be a natural number with , let be the real numbers with the order of its ordered field structure, let be a point of Euclidean space , regarded as a real vector space by Euclidean Space is a Real Vector Space, and…Testing a Block Semidefinite Inequality on the Diagonal
lemmalem:block-order-implies-matrix-order-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number with , let be the real numbers, let , and let and be symmetric real matrices. Write for the identity matrix of size , write for the real matrix all of whose entrie…The Quadratic Form of a Real Square Matrix is Bounded on the Closed Unit Ball
lemmalem:matrix-quadratic-form-bounded-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number with , let be the initial segment determined by , and let be the real numbers with the order of its ordered field structure and the absolute value . Let be a real matrix, with entries…Action and Quadratic Form of a Block Matrix
lemmalem:block-matrix-quadratic-form-2026aAnalysisLinear AlgebraMultivariable CalculusLet and be natural numbers with and , let be the real numbers, and for a natural number let be the initial segment determined by . Let , , and be real matrices of sizes , , and…Convex Combination of Finitely Many Points of
definitiondef:convex-combination-rn-2026aAnalysisLinear AlgebraMultivariable CalculusLet and be natural numbers with and , let be the real numbers with the order of its ordered field structure, and let and be the initial segments determined by and by . Let be a family of points…A Function of Class with Positive Semidefinite Hessian is Convex
theoremthm:hessian-psd-implies-convex-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number and let be the real numbers. Let be an open and convex subset of Euclidean space , a real vector space by Euclidean Space is a Real Vector Space, and let be…Derivatives of the Slice of a Function Along a Line
lemmalem:line-slice-derivative-2026bAnalysisMultivariable CalculusLet be a natural number, let be the real numbers, and let be an open subset of Euclidean space . Write for the dot product of points of and for the matrix-vector product. Let be…A Semiconvex Function of Class has Hessian Bounded Below by
corollarycor:semiconvex-c2-hessian-bound-2026aAnalysisPDEMultivariable CalculusLet be a natural number and let be the real numbers. Let be an open and convex subset of Euclidean space , a real vector space by Euclidean Space is a Real Vector Space, let satisfy…