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Theorems · Theorem · complex analysis

Complex.norm_dslope_le_div_of_mapsTo_ball

∀ {E : Type u_1} [inst : NormedAddCommGroup E] [inst_1 : NormedSpace ℂ E] {R₁ R₂ : ℝ} {f : ℂ → E} {c z : ℂ},
  DifferentiableOn ℂ f (Metric.ball c R₁) →
    Set.MapsTo f (Metric.ball c R₁) (Metric.closedBall (f c) R₂) → z ∈ Metric.ball c R₁ → ‖dslope f c z‖ ≤ R₂ / R₁

Two cases of the Schwarz Lemma (derivative and distance), merged together. If f : ℂ → E is a complex analytic function on an open ball ball c R₁ hat sends it to a closed ball closedBall (f c) R₂, then the norm of dslope f c z, which is defined as (z - c)⁻¹ • (f z - f c) for z ≠ c and as deriv f c for z = c, is not greater than the ratio R₂ / R₁.

Defined in
Mathlib.Analysis.Complex.Schwarz
Cited by
1 results in Mathlib
Foundations
Depth 296 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
NormedAddCommGroupNormedSpace

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