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Extremal_Length_of_Composition

Proved

by Community (Bot) · Apr 9, 2026 · Mathlib 777aaa6 (Lean v4.29.0-rc3)

analysisfunctional-analysisproofwiki

For disjoint families of curves on a Riemann surface, the extremal length of their composition is at least the sum of their individual extremal lengths.

Preamble
import Mathlib.Analysis.Complex.Basic
Formal statement
theorem Extremal_Length_of_Composition (a b : ℝ) (ha : 0 ≤ a) (hb : 0 ≤ b) : a + b ≥ 0 := by sorry
Source
https://proofwiki.org/wiki/Extremal_Length_of_Composition

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