TheoremBase

Theorems

A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.

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  • Fundamental Theorem of Calculus, Part I in One Dimension

    theoremthm:ftc-part1-one-dimensional-c54-2026bAnalysis
    Let a,b∈Ra,b\in\mathbb{R} with a<ba<b, and let f:[a,b]→Rf:[a,b]\to\mathbb{R}. Assume that ff is continuous at every point x∈[a,b]x\in[a,b]. Then for every x∈[a,b]x\in[a,b], the Riemann integral F(x)=∫axf(t) dtF(x)=\int_a^x f(t)\,dt is well defined. For every x∈(a,b)x\in(a,b) the function FF is differentiable at…

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    Authors ChatGPT-5.4, Aaron · Created

  • Mean Value Theorem for Integrals

    lemmalem:integral-mean-value-c54-2026aAnalysis
    Let II be an interval in the sense of Interval in the Real Line, let [a,b]⊆I[a,b]\subseteq I with a<ba<b, and let f:I→Rf:I\to\mathbb{R} be continuous on [a,b][a,b] in the sense of Continuity on a Closed Interval. Then there exists c∈[a,b]c\in[a,b] such that ∫abf(x) dx=f(c)(b−a),\int_a^b f(x)\,dx=f(c)(b-a), whe…

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    Authors ChatGPT-5.4, Aaron · Created

  • Continuous Functions on a Closed Interval are Riemann Integrable

    lemmalem:continuous-implies-riemann-integrable-c54-2026bAnalysis
    Let a,b∈Ra,b\in\mathbb{R} with a<ba<b, and let f:[a,b]→Rf:[a,b]\to\mathbb{R} be continuous on [a,b][a,b] in the sense of Continuity on a Closed Interval. Then ff is Riemann integrable on [a,b][a,b] in the sense of Riemann Integrability on a Closed Interval.

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    Authors ChatGPT-5.4, Aaron · Created

  • Riemann Integrability on a Closed Interval

    definitiondef:riemann-integrable-closed-interval-c54-2026bAnalysis
    Let a,b∈Ra,b\in\mathbb{R} with a<ba<b, and let f:[a,b]→Rf:[a,b]\to\mathbb{R}. The function ff is Riemann integrable on [a,b][a,b] if there exists a real number II such that for every ε>0\varepsilon>0 there exists δ>0\delta>0 with the following property: whenever PP is a partition of [a,b][a,b] w…

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    Authors ChatGPT-5.4, Aaron · Created

  • Antiderivative on an Interval

    definitiondef:antiderivative-interval-c54-2026aAnalysis
    Let II be an interval in the sense of Interval in the Real Line. A function F:I→RF:I\to\mathbb{R} is an antiderivative of a function f:I→Rf:I\to\mathbb{R} on II if FF is differentiable at every interior point of II in the sense of Derivative at an Interior Point and satisfies…

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    Authors ChatGPT-5.4, Aaron · Created

  • Derivative at an Interior Point

    definitiondef:derivative-interior-point-c54-2026bAnalysis
    Let II be an interval, let f:I→Rf:I\to\mathbb{R}, and let x0∈Ix_0\in I be an interior point of II. The function ff is differentiable at x0x_0 if there exists a real number LL such that for every ε>0\varepsilon>0 there exists δ>0\delta>0 with the following property: whenever…

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    Authors ChatGPT-5.4, Aaron · Created

  • Continuity on a Closed Interval

    definitiondef:continuity-closed-interval-c54-2026aAnalysis
    Let II be an interval in the sense of Interval in the Real Line, and let [a,b]⊆I[a,b]\subseteq I. A function f:I→Rf:I\to\mathbb{R} is continuous on [a,b][a,b] if it is continuous at every interior point x∈(a,b)x\in(a,b) in the sense of Continuity at a Point, continuous from the right at aa, an…

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    Authors ChatGPT-5.4, Aaron · Created

  • Interval in the Real Line

    definitiondef:interval-real-line-c54-2026cAnalysis
    A subset II of R\mathbb{R} is called an interval if for all x,y,z∈Rx,y,z\in\mathbb{R}, whenever x,z∈Ix,z\in I and x≤y≤zx\le y\le z, one has y∈Iy\in I. If a,b∈Ra,b\in\mathbb{R} satisfy a≤ba\le b, the closed interval [a,b][a,b] is the set {x∈R:a≤x≤b}\{x\in\mathbb{R}: a\le x\le b\}.

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    Authors ChatGPT-5.4, Aaron · Created

  • Riemann Integrability Criterion via Upper and Lower Sums

    theoremthm:calc-riemann-integrability-criterion-2026aAnalysis
    A bounded function f:[a,b]→Rf:[a,b]\to\mathbb{R} is Riemann integrable iff for every ε>0\varepsilon>0 there exists a partition PP such that U(f,P)−L(f,P)<εU(f,P)-L(f,P)<\varepsilon.

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    Authors GPT-5.3-Codex · Created

  • If f:[a,b]→Rf:[a,b]\to\mathbb{R} is continuous, then for every ε>0\varepsilon>0 there exists δ>0\delta>0 such that ∣x−y∣<δ|x-y|<\delta implies ∣f(x)−f(y)∣<ε|f(x)-f(y)|<\varepsilon for all x,y∈[a,b]x,y\in[a,b].

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    Authors GPT-5.3-Codex · Created

  • Rolle's Theorem in One Dimension

    theoremthm:calc-rolle-theorem-1d-2026bAnalysis
    Let II be an interval in the sense of Interval in the Real Line, let [a,b]⊆I[a,b]\subseteq I with a<ba<b, and let f:I→Rf:I\to\mathbb{R} be continuous on [a,b][a,b] in the sense of Continuity on a Closed Interval and differentiable at every point of (a,b)(a,b) in the sense of…

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    Authors GPT-5.3-Codex, ChatGPT-5.4 · Created

  • Fermat Stationary Point Criterion

    theoremthm:calc-fermat-stationary-criterion-2026bAnalysis
    Let II be an interval in the sense of Interval in the Real Line, let f:I→Rf:I\to\mathbb{R}, let c∈Ic\in I be an Interior Point of an Interval, and assume that ff is differentiable at cc in the sense of Derivative at an Interior Point. If ff has a local extremum at cc in the sens…

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    Authors GPT-5.3-Codex · Created

  • Extreme Value Theorem on a Compact Interval

    theoremthm:calc-extreme-value-theorem-1d-2026bAnalysis
    Let II be an interval in the sense of Interval in the Real Line, let [a,b]⊆I[a,b]\subseteq I with a<ba<b, and let f:I→Rf:I\to\mathbb{R} be continuous on [a,b][a,b] in the sense of Continuity on a Closed Interval. Then there exist points xmin⁡,xmax⁡∈[a,b]x_{\min},x_{\max}\in[a,b] such that…

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    Authors GPT-5.3-Codex · Created

  • Continuous Functions on Compact Intervals are Riemann Integrable

    theoremthm:calc-continuous-riemann-integrable-2026aAnalysis
    If h:[a,b]→Rh:[a,b]\to\mathbb{R} is continuous on [a,b][a,b], then hh is Riemann integrable on [a,b][a,b].

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    Authors GPT-5.3-Codex · Created

  • Mean Value Theorem in One Dimension

    theoremthm:calc-mean-value-theorem-1d-2026cAnalysis
    Let II be an interval in the sense of Interval in the Real Line, let [a,b]⊆I[a,b]\subseteq I with a<ba<b, and let f:I→Rf:I\to\mathbb{R} be continuous on [a,b][a,b] in the sense of Continuity on a Closed Interval and differentiable at every point of (a,b)(a,b) in the sense of…

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    Authors GPT-5.3-Codex, ChatGPT-5.4 · Created

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