Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Distance from a Point to a Nonempty Subset of a Metric Space
definitiondef:distance-point-to-set-2026aAnalysisTopologyLet be a metric space, let be nonempty, and let . Let where denotes the real numbers. Then is nonempty because is, and is a lower bound for…Uniformly Continuous Map Between Metric Spaces
definitiondef:uniformly-continuous-metric-2026bAnalysisTopologyDefines uniform continuity of a map from a subset of a metric space into a metric space: one delta serves every pair of points for a given epsilon.The Closure of a Bounded Subset of is Compact
corollarycor:closure-bounded-rn-compact-2026aAnalysisTopologyMultivariable CalculusLet be a natural number, let be the Euclidean distance on Euclidean space , which is a metric by with the Euclidean Distance Is a Complete Metric Space with Coordinatewise Convergence, and let be the collection of subsets…The Closure of a Bounded Subset of a Metric Space is Bounded
lemmalem:closure-bounded-metric-2026aAnalysisTopologyLet be a metric space, and let be the collection of all subsets of that are open in , which is a topology on by The Open Subsets of a Metric Space Form a Topology. Let be bounded in . Then the closure…Sequential Characterization of the Closure in a Metric Space
lemmalem:closure-sequential-characterization-metric-2026aAnalysisTopologyLet be a metric space, and let be the collection of all subsets of that are open in , which is a topology on by The Open Subsets of a Metric Space Form a Topology. Let , let , and let denote the…Characterization of the Closure in a Metric Space by Open Balls
theoremthm:closure-metric-characterization-2026aAnalysisTopologyLet be a metric space, and let be the collection of all subsets of that are open in , which is a topology on by The Open Subsets of a Metric Space Form a Topology. Let and let . Then the following are equivalent. 1.…- A closed interval [a,b] of real numbers is compact in the topology of the real line given by the metric |s - t|.
Compact Subset of is Bounded
theoremthm:compact-subset-rn-bounded-2026bAnalysisTopologyMultivariable CalculusLet be a natural number, let be the Euclidean distance on Euclidean space , which is a metric by with the Euclidean Distance Is a Complete Metric Space with Coordinatewise Convergence, and let be the collection of subsets…Compact Subset of is Closed
theoremthm:compact-subset-rn-closed-2026bAnalysisTopologyMultivariable CalculusLet be a natural number, let be the Euclidean distance on Euclidean space , which is a metric by with the Euclidean Distance Is a Complete Metric Space with Coordinatewise Convergence, and let be the collection of subsets…- A sequence in a metric space converges to at most one point.
Bolzano-Weierstrass Theorem in Euclidean Space
theoremthm:bolzano-weierstrass-rn-2026aAnalysisMultivariable CalculusLet be a natural number and let be Euclidean space equipped with the Euclidean distance , which is a metric by with the Euclidean Distance Is a Complete Metric Space with Coordinatewise Convergence. Let be bounded in…Convergence in Euclidean Space is Coordinatewise Convergence
lemmalem:convergence-coordinatewise-rn-2026aAnalysisMultivariable CalculusLet be a natural number, let be the initial segment of determined by , and let be Euclidean space equipped with the Euclidean distance , which is a metric by…Coordinate Bounds Control the Euclidean Norm
lemmalem:euclidean-norm-coordinate-bound-2026aAnalysisMultivariable CalculusLet be a natural number, let be the initial segment of determined by , and let be a point of Euclidean space . Write for the Euclidean norm, for the absolute value on the real numbers, w…- Let denote the real numbers, with the addition, multiplication, additive identity and multiplicative inverses of the underlying field and with the order of its ordered field structure; for write to mean and…
Properties of the Canonical Map from the Natural Numbers to an Ordered Field
lemmalem:natural-number-image-properties-2026bAnalysisAlgebraThe canonical map from the natural numbers to an ordered field sends 1 to 1 and successors to successors, is additive, multiplicative, at least 1, positive, strictly increasing and injective.A Closed Interval is Sequentially Compact in the Real Line
theoremthm:closed-interval-sequentially-compact-real-2026aAnalysisTopologyLet denote the real numbers, with the order of its ordered field structure, and let be the real line, that is, equipped with the absolute value metric. Let satisfy , and let be the…A Totally Bounded Subset of a Nonempty Metric Space is Bounded
lemmalem:totally-bounded-implies-bounded-metric-2026aAnalysisTopologyLet be a metric space whose underlying set is nonempty, and let be totally bounded in . Then is bounded in .Sequential Characterization of Closed Subsets of a Metric Space
lemmalem:sequentially-closed-metric-2026aAnalysisTopologyLet be a metric space, and let be the collection of all subsets of that are open in , which is a topology on by The Open Subsets of a Metric Space Form a Topology. Let , and let denote the natural numbers. Then…A Subsequence of a Subsequence is a Subsequence
lemmalem:subsequence-of-subsequence-2026aAnalysisSet TheoryLet be the set of natural numbers with the order of that definition, let be a set, let be a sequence in , and let and be sequences in that are strictly increasing. Then…- Let be a natural number, let be the Euclidean distance on Euclidean space , which is a metric by with the Euclidean Distance Is a Complete Metric Space with Coordinatewise Convergence, and let be the collection of subsets…