Theorems · Theorem · real analysis

strictMonoOn_of_hasDerivWithinAt_pos

∀ {D : Set ℝ},
  Convex ℝ D →
    ∀ {f f' : ℝ → ℝ},
      ContinuousOn f D →
        (∀ x ∈ interior D, HasDerivWithinAt f (f' x) (interior D) x) → (∀ x ∈ interior D, 0 < f' x) → StrictMonoOn f D

Let f be a function continuous on a convex (or, equivalently, connected) subset D of the real line. If f is differentiable on the interior of D and f' is strictly positive, then f is a strictly monotone function on D.

Defined in

Mathlib.Analysis.Calculus.Deriv.MeanValue

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Foundations

Depth 191 from the axioms · uses propext, Classical.choice, Quot.sound