/- Copyright 2025 The Formal Conjectures Authors. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at https://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. -/ module public import Batteries.Data.Nat.Gcd public import Mathlib.Algebra.GCDMonoid.Finset public import Mathlib.Algebra.GCDMonoid.Nat@[expose] public section

A Finset of numbers is coprime, or relatively prime, if its gcd is 1.

@[reducible] def Finset.Coprime (S : Finset ) : Prop := S.gcd id = 1theorem Finset.Coprime_pair_iff (S : Finset ) (a b : ) (h : S = {a, b}) : S.Coprime Nat.Coprime a b := S:Finset a:b:h:S = {a, b}S.Coprime a.Coprime b S:Finset a:b:h:S = {a, b}GCDMonoid.gcd (id a) (id b) = 1 a.gcd b = 1 All goals completed! 🐙