Proof of the Cauchy mean value theorem from Rolle's theorem
Builds on Rolle's theoremContinuous functionConstant multiple rule
Proof
We apply Rolle's theorem to a suitable linear combination of and .
- Let and . These are real constants.
- Define by .
- A linear combination of continuous functions is continuous, so is continuous on .
- By the sum and constant multiple rule, is differentiable on with .
- Expanding, .
- Expanding, .
- So . By Rolle's theorem, there is with .
- By step 4, . That is, .
Idea
The coefficients of make the endpoint values of and cancel, so . Rolle's theorem then gives a point where . At that point the claimed relation between and holds.
Reading path
To understand this page from the ground up, read these 134 pages in order. The foundations come first. The path takes the proofs Proof of the limit of a sum of sequences, Proof of Rolle's theorem, Proof of the approximation property of the supremum, Proof that every sequence has a monotone subsequence, by peaks, Proof of the commutativity of addition by induction, Proof of the epsilon-delta form of continuity, Proof that there is a natural number n with 1/n below any positive epsilon, Proof that the reals form an ordered field, with the Cauchy sequence construction, Proof of the double negation law by a truth table, Proof of the extreme value theorem by the Bolzano–Weierstrass theorem, Proof of the uniqueness of limits, Proof of strong induction from ordinary induction, Proof of the limit of a product of sequences, Proof that the absolute value is multiplicative, Proof of the squeeze theorem for sequences, Proof of the linearity of differentiation, Proof of the sequential characterization of limits, Proof of the triangle inequality for real numbers, Proof of the epsilon-N definition of the limit of a sequence, Proof of Fermat's theorem on stationary points, Proof that limits preserve non-strict inequalities, Proof of the epsilon-delta form of the limit of a function, Proof of the well-ordering principle from strong induction, Proof of the Bolzano–Weierstrass theorem by a monotone subsequence, Proof of the Archimedean property in an Archimedean ordered field, Proof that a decreasing sequence bounded below converges, Proof that the reals are Archimedean from the completeness axiom, Proof that convergent sequences are bounded, Proof of the monotone convergence theorem for sequences, Proof that continuity is equivalent to sequential continuity, Proof of the boundedness theorem by Bolzano–Weierstrass, Proof of the constant multiple rule.
- Construction of the reals from Cauchy sequences concept
- Definition by recursion concept
- Element definition
- Integers object
- Limit point of a set definition
- Local maximum definition
- Mathematical induction concept
- Natural numbers object
- Ordered field definition
- Peano axioms concept
- Proposition concept
- Rational numbers object
- Real numbers object
- Sequence definition
- Set bounded above definition
- Set definition
- Ring of integers statement
- Limit of a function definition
- Local minimum definition
- Archimedean ordered field definition
- Successor function definition
- Conjunction definition
- Disjunction definition
- Implication definition
- Negation definition
- Predicate definition
- The reals form a field statement
- Real sequence definition
- Subsequence definition
- Infimum definition
- Supremum definition
- Ordered pair definition
- Continuity at a point definition
- Derivative definition
- Addition of natural numbers definition
- Proof of the Archimedean property in an Archimedean ordered field proof
- The rationals form a field statement
- Biconditional definition
- The successor function is injective statement
- Zero is not a successor statement
- Truth table concept
- Modus ponens concept
- Universal quantifier definition
- Bounded sequence definition
- Limit of a sequence definition
- Monotone sequence definition
- Completeness axiom statement
- Cartesian product definition
- Continuous function definition
- Differentiable function definition
- Archimedean property statement
- Proof of the commutativity of addition by induction proof
- Order on the natural numbers definition
- Subset definition
- The rationals form an ordered field statement
- Propositional logic concept
- Mathematical proof concept
- Convergent sequence definition
- Sequential continuity definition
- Binary relation definition
- Order on the reals definition
- Commutativity of addition statement
- Proof of strong induction from ordinary induction proof
- Tautology definition
- Antisymmetric relation definition
- Reflexive relation definition
- Transitive relation definition
- Interval definition
- Strong induction statement
- Logical equivalence definition
- Preorder definition
- Proof of the epsilon-delta form of continuity proof
- Proof of the epsilon-delta form of the limit of a function proof
- Proof of the well-ordering principle from strong induction proof
- Proof of the double negation law by a truth table proof
- Partial order definition
- Epsilon-delta definition of continuity statement
- Epsilon-delta definition of a limit statement
- Well-ordering principle statement
- Double negation law statement
- Total order definition
- Proof by contradiction concept
- Proof that every sequence has a monotone subsequence, by peaks proof
- Proof that the reals form an ordered field, with the Cauchy sequence construction proof
- Every sequence has a monotone subsequence statement
- The reals form an ordered field statement
- Absolute value definition
- Proof of the approximation property of the supremum proof
- Proof of the triangle inequality for real numbers proof
- Proof that the absolute value is multiplicative proof
- Proof of the epsilon-N definition of the limit of a sequence proof
- Approximation property of the supremum statement
- Triangle inequality statement
- Absolute value is multiplicative statement
- Epsilon-N definition of the limit of a sequence statement
- Proof that the reals are Archimedean from the completeness axiom proof
- Proof of the limit of a sum of sequences proof
- Proof of the squeeze theorem for sequences proof
- Proof of the uniqueness of limits proof
- Proof that limits preserve non-strict inequalities proof
- The reals are Archimedean statement
- Proof that convergent sequences are bounded proof
- Proof of the monotone convergence theorem for sequences proof
- Proof that there is a natural number n with 1/n below any positive epsilon proof
- Limit of a sum of sequences statement
- Uniqueness of limits statement
- Limits preserve non-strict inequalities statement
- Squeeze theorem statement
- Convergent sequences are bounded statement
- Monotone convergence theorem for sequences statement
- Proof of the limit of a product of sequences proof
- There is a natural number n with 1/n below any positive epsilon statement
- Proof that a decreasing sequence bounded below converges proof
- Decreasing sequence bounded below converges statement
- Proof of the sequential characterization of limits proof
- Proof that continuity is equivalent to sequential continuity proof
- Limit of a product of sequences statement
- Continuity is equivalent to sequential continuity statement
- Sequential characterization of limits statement
- Proof of the Bolzano–Weierstrass theorem by a monotone subsequence proof
- Proof of the linearity of differentiation proof
- Bolzano–Weierstrass theorem statement
- Linearity of differentiation statement
- Proof of the boundedness theorem by Bolzano–Weierstrass proof
- Proof of the constant multiple rule proof
- Boundedness theorem statement
- Constant multiple rule statement
- Proof of the extreme value theorem by the Bolzano–Weierstrass theorem proof
- Extreme value theorem statement
- Proof of Fermat's theorem on stationary points proof
- Fermat's theorem on stationary points statement
- Proof of Rolle's theorem proof
- Rolle's theorem statement
- Proof of the Cauchy mean value theorem from Rolle's theorem proof
Where this leads
37 pages build on this one.
- Cauchy mean value theorem
- Taylor's theorem with the Peano remainder
- Taylor's theorem
- De Moivre–Laplace theorem
- Central limit theorem
- Taylor's theorem with the Lagrange remainder
- L'Hôpital's rule
- Characteristic function of the normal distribution
- Sum of independent normal random variables
- Hoeffding's inequality
- Proof of Taylor's theorem by repeated use of L'Hôpital's rule
- Koksma–Hlawka inequality
- McDiarmid's inequality
- Asymptotic normality of the maximum likelihood estimator
- Edgeworth expansion
- Quadratic convergence of Newton's method
- Proof of Hoeffding's inequality via Hoeffding's lemma and the Chernoff bound
- Azuma's inequality
- Erdős–Kac theorem
- Proof of the de Moivre–Laplace theorem from the central limit theorem
- Monte Carlo integration
- Delta method
- Proof of the sum of independent normal random variables by characteristic functions
- Proof of the central limit theorem by characteristic functions
- Berry–Esseen theorem
- Ideal chain
- Proof of the formula for the characteristic function of the normal distribution
- Proof of Taylor's theorem with the Lagrange remainder by the Cauchy mean value theorem
- Finite difference coefficients
- Flory–Huggins solution theory
- Proof of Taylor's theorem with the Peano remainder
- Proof of L'Hôpital's rule from the Cauchy mean value theorem
- Heun's method
- Reptation
- Midpoint method
- Monte Carlo methods in finance
- Worm-like chain
Further reading
- Web https://en.wikipedia.org/wiki/Mean_value_theorem, Cauchy's mean value theorem
About this page
| Tag | GN1S16Y6AG |
|---|---|
| URI | m2://GN1S16Y6AG |
| Kind | proof |
| Writing | W0 stub |
| MSC | 26A24 |
| Proves | Cauchy mean value theorem |
| Uses | Rolle's theorem, Continuous function, Constant multiple rule |
| Changed | 4 November 2026 |
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