Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site watdaisy.UUCP
Path: utzoo!watmath!watdaisy!ndiamond
From: ndiamond@watdaisy.UUCP (Norman Diamond)
Newsgroups: net.puzzle
Subject: Re: More on Interview Questions.
Message-ID: <7118@watdaisy.UUCP>
Date: Sun, 24-Mar-85 16:26:43 EST
Article-I.D.: watdaisy.7118
Posted: Sun Mar 24 16:26:43 1985
Date-Received: Mon, 25-Mar-85 02:11:54 EST
References: <379@cavell.UUCP> <917@utcsri.UUCP> <7115@watdaisy.UUCP>
Distribution: net
Organization: U of Waterloo, Ontario
Lines: 30

> 		Let    y(x) = x!
> 			y(x+1) = (x+1)!
> 
> 			(let  deltax = 1)
> 			dy/dx  =  limit as deltax -> 0 of 
> 					(y(x+deltax)-y(x)) / (deltax)
> 				= { y(x+1) - y(x) } / {(x+1)-x}
> 				= { (x+1)! - x! } / 1
> 				= (x+1) x! - x!
> 				= x x! + x! - x!
> 				= x * x!
> 	That is,  the derivative of  x!  is  x * x!

Limit as deltax -> 0, but let deltax = 1?
Is this, then, the limit as 1 -> 0?

dy/dx = limit as deltax -> 0 of
        { (x+deltax) (x+deltax-1)!  -  x! } / {deltax}

        most of those deltax samples will be much smaller than 1.

-- 

   Norman Diamond

UUCP:  {decvax|utzoo|ihnp4|allegra}!watmath!watdaisy!ndiamond
CSNET: ndiamond%watdaisy@waterloo.csnet
ARPA:  ndiamond%watdaisy%waterloo.csnet@csnet-relay.arpa

"Opinions are those of the keyboard, and do not reflect on me or higher-ups."