dy/dx

With reference to my previous answer.http://hk.knowledge.yahoo.com/question/question?qid=7008091301670


圖片參考：http://i295.photobucket.com/albums/mm158/Audrey_hepburn2008/A_Hepburn01Sep141216.jpg?t=1221365784

Now, y = logx is in fact y = log10x

So, we put a = 10

dy/dx of y = logx is 1 / (xln10)