s_comp_π_0 — Mathlib

English

The composite of s with base equals the base map.

Русский

Сложение s с базовой мap эквивалентно базовой map.

LaTeX

$$$ s_n \circ Base = Base $$$

Lean4

theorem s_comp_π_0 (n : ℕ) :
    ExtraDegeneracy.s f S n ≫ WidePullback.π _ 0 =
      @WidePullback.base _ _ _ f.right (fun _ : Fin (n + 1) => f.left) (fun _ => f.hom) _ ≫ S.section_ :=
  by
  dsimp [ExtraDegeneracy.s]
  simp
    -- Porting note (https://github.com/leanprover-community/mathlib4/issues/11119): @[simp] removed as the linter complains the LHS is not in normal form

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