23/04/05 21:06:20.43 Lto72acu.net
>>6 追加
結合則が成り立つ場合
左反転と右反転は、一致します（下記）
証明は
「l=l*(x*r)=(l*x)*r=r」です
覚えておきましょう！
(参考)
URLﾘﾝｸ(en.wikipedia.org)
Inverse element
Inverses
An element is invertible under an operation if it has a left inverse and a right inverse.
In the common case where the operation is associative, the left and right inverse of an element are equal and unique.
Indeed, if l and r are respectively a left inverse and a right inverse of x, then
l=l*(x*r)=(l*x)*r=r.
The inverse of an invertible