Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
- Every bounded sequence of real numbers has a subsequence that converges to a real number in the sense of Limit of a Sequence of Real Numbers.
- Let be a sequence of real numbers. A subsequence of is a sequence of the form , where is a strictly increasing sequence of positive integers.
- A sequence of real numbers is called bounded if there exists a real number such that
- Let with , and let . Suppose that has a local extremum at an interior point and that is differentiable at . Then
- Let with , and let be continuous at every point in . Then there exist points such that
- Let be an interval in the sense of Interval in the Real Line, let , and let . One says that has a local extremum at if either has a local maximum at or has a local minimum at ; that is, there exists such that for eve…
Every Cauchy Sequence of Real Numbers Converges
theoremthm:cauchy-sequence-converges-real-c54-2026aAnalysisEvery Cauchy sequence of real numbers converges to a real number in the sense of Limit of a Sequence of Real Numbers.- A sequence of real numbers is called a Cauchy sequence if for every there exists such that for all integers ,
- Let be a sequence of real numbers, and let . One says that converges to if for every there exists such that for all integers , In that case one writes…
Continuity on a Closed Interval Implies Uniform Continuity
lemmalem:heine-cantor-closed-interval-c54-2026aAnalysisLet with . If is continuous on , then is uniformly continuous on .Upper and Lower Darboux Sums of a Bounded Function on a Partition
definitiondef:darboux-sums-2026aAnalysisFor a bounded f on [a,b] and a partition a=x_1<...<x_{n+1}=b, the upper and lower bound maps take the supremum and the infimum of f on each [x_i,x_{i+1}], and the upper and lower sums weight them by the lengths of these intervals and add them up.Least Upper Bound Property of the Real Numbers
definitiondef:least-upper-bound-property-c54-2026aAnalysisThe real numbers have the least upper bound property: whenever is nonempty and bounded above, there exists a number such that .- Let . A number is called a lower bound of if for every . If is nonempty and bounded below, then a number is called the greatest lower bound, or infimum, of if:…
Uniform Continuity on a Subset of the Real Numbers
definitiondef:uniform-continuity-real-subset-c54-2026aAnalysisLet and let . The function is said to be uniformly continuous on if for every there exists such that for all , if , thenAdditivity of the Riemann Integral over Adjacent Intervals, Subintervals and Oriented Integrals, and Integrals of Restrictions
lemmalem:riemann-integral-additivity-2026aAnalysisA bounded function is integrable on [a,b] exactly when it is integrable on [a,c] and [c,b], and then the integrals add; integrability passes to closed subintervals, and oriented integrals satisfy the additivity rule for any three points.- Let with , let , let be a partition of , and let determine a tagged partition of relative to . The corresponding Riemann sum of is the real number…
Tagged Partition of a Closed Interval
definitiondef:tagged-partition-closed-interval-c54-2026aAnalysisLet with , and let be a partition of . A tagged partition of relative to is a choice of points for each .Partitions of a Closed Interval, the Set of Partitions, and Refinements
definitiondef:partition-closed-interval-2026aAnalysisA partition of [a,b] (a<b) is a finite subset of [a,b] containing a and b; the partitions of [a,b] form a set, and Q refines P when P is contained in Q.- Let be an interval. A point is an interior point of if there exist points such that .
- Let be a set. A total order on is a binary relation on , equivalently a subset of , and we write to mean that . The relation is a total order if the following axioms hold. 1. For every , one has . [Reflexivi…