精華區beta Math 關於我們 聯絡資訊
Let f:S→T and g:T→U be bijections. Show that g。f is a bijection and -1 -1 -1 (g。f) = f 。 g . -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 220.136.220.39