Proof the following:
圖片參考:http://i165.photobucket.com/albums/u61/henrywan910/math_knowledge/MSP6312195ge934cgf4id55000028803h3c.gif
收錄日期: 2021-04-22 00:41:09
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20090517000051KK01012