ࣸ૾ ࣸ૾ f : A → B ͕ࣸ૾Ͱ͋ΔͱɺҎԼͷ݅Λຬͨ͢ͱ͖ʹݴ͏ ҙͷ a ∈ A ʹରͯ͠ɺ f(a) ∈ B ͕ඞͣଘࡏ͢Δ a ∈ A ʹରͯ͠ f(a) ∈ B ͨͩͻͱͭʹఆ·Δ f(a) Λ a ͷ૾ͱ͍͏ɻશͯͷ a ∈ A ʹରͯ͠૾͕ଘࡏ͢Δ͜ͱΛڧௐͯ͠શҬࣸ૾ͱ ͍͏͜ͱ͋ΔɻҰൠʹࣸ૾ͱ͍͏ͱ͖શҬࣸ૾Λࢦ͢ɻ ٯʹɺ A ͷ෦ू߹ͷΈʹ͔͠ f(a) ͕ଘࡏ͠ͳ͍ʢఆٛ͞Ε͍ͯͳ͍ʣࣸ૾Λ෦ࣸ ૾ͱ͍͏ɻ ٯࣸ૾ ࣸ૾ f : A → B ʹର͠ɺ ࣸ૾ g : B → A ͕ଘࡏͯ͠ ∀a ∈ A, g(f(a)) = a ͱͳΔͱ͖ɺ g Λ f ͷٯࣸ૾ͱ͍͍ɺ f−1 ͱॻ͘ɻ ܂ാӳࢿ (@mather314) ฏͷֶษڧձ 2 ճ 2017/10/24 13 / 15