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Re: Log Error

  • To: mathgroup at smc.vnet.net
  • Subject: [mg78866] Re: Log Error
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Wed, 11 Jul 2007 06:17:48 -0400 (EDT)

On 7/10/07 at 6:27 AM, L_Kohn at Nesbittgraphics.com (Laurence Kohn)
wrote:

>I had a question about something I found in Mathematica 5.2...   I
>was plotting Log[x-1]-2 with x = {0,10} and y =  {-10,5} and
>strangely found that the graph crossed the x-axes at approximately x
>== 8  ...

>It should be 101 of course, but it seemed like 8.   Then I did an
>Nsolve with the equation set to 0, and low and behold got an answer
>x == 8.38906.

>Is this a bug in mathematica or am I missing something here?

In Mathematica Log[x] is the natural logarithm of x not the
logarithm base 10. That would be written Log[10,x].

So,

NSolve[Log[10,x-1]==2,x]

will give you 101. as you are expecting
--
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