Re: Re: Log Error ( ? )
- To: mathgroup at smc.vnet.net
- Subject: [mg78991] Re: [mg78945] Re: [mg78883] Log Error ( ? )
- From: Murray Eisenberg <murray at math.umass.edu>
- Date: Sat, 14 Jul 2007 02:50:15 -0400 (EDT)
- Organization: Mathematics & Statistics, Univ. of Mass./Amherst
- References: <200707120911.FAA08031@smc.vnet.net> <200707131007.GAA11804@smc.vnet.net>
- Reply-to: murray at math.umass.edu
After posting my response, below, I saw another response indicating that
you need to use Log[10,x] for the common (base-10) logarithm.
Sorry for not catching that possibility. To a mathematician, log always
means natural base (E) logarithm. By contrast, to an engineer, log
often means base 10, whereas ln denotes the natural logarithm. (And so
nearly all calculus books, kowtowing to the predilections of engineers,
use "ln".)
Of course to a computer scientist, log would more often mean the base-2
logarithm!
Murray Eisenberg wrote:
> Umm...
>
> Log[x-1]-2 = 0
>
> is equivalent to x = 1+E^2, and N[1+E^2] gives 8.38906.
>
> Only "bug" is in your thinking the intercept should be 101.
>
> Larry wrote:
>> Hi,
>>
>> 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?
>>
>
--
Murray Eisenberg murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower phone 413 549-1020 (H)
University of Massachusetts 413 545-2859 (W)
710 North Pleasant Street fax 413 545-1801
Amherst, MA 01003-9305
- References:
- Log Error ( ? )
- From: Larry <ldk545@hotmail.com>
- Re: Log Error ( ? )
- From: Murray Eisenberg <murray@math.umass.edu>
- Log Error ( ? )