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removing HasMul
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hannahfechtner committed Oct 23, 2024
1 parent 5455d64 commit c336c4f
Showing 1 changed file with 2 additions and 3 deletions.
5 changes: 2 additions & 3 deletions Mathlib/GroupTheory/Congruence/Basic.lean
Original file line number Diff line number Diff line change
Expand Up @@ -298,9 +298,8 @@ lemma comapQuotientEquivOfSurj_symm_mk (c : Con M) {f : N →* M} (hf : Function
/-- This version infers the surjectivity of the function from a MulEquiv function -/
@[simp]
lemma comapQuotientEquivOfSurj_symm_mk' (c : Con M) (f : N ≃* M) (x : N) :
((@MulEquiv.symm (Con.Quotient (comap ⇑f _ c)) _ (hasMul (comap ⇑f _ c))
_ (comapQuotientEquivOfSurj c ↑f f.surjective))
⟦f x⟧) = ↑x :=
((@MulEquiv.symm (Con.Quotient (comap ⇑f _ c)) _ _ _
(comapQuotientEquivOfSurj c f f.surjective)) ⟦f x⟧) = ↑x :=
(MulEquiv.symm_apply_eq (@comapQuotientEquivOfSurj M N _ _ c f _)).mpr rfl

/-- The **second isomorphism theorem for monoids**. -/
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