Re: Log Error
- To: mathgroup at smc.vnet.net
- Subject: [mg78830] Re: Log Error
- From: dimitris <dimmechan at yahoo.com>
- Date: Wed, 11 Jul 2007 05:58:40 -0400 (EDT)
- References: <f6vnds$qfr$1@smc.vnet.net>
Laurence Kohn :
> 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?
I don't understand your problem...
In[14]:=
Flatten[{Solve[Log[x - 1] - 2 == 0, x], Reduce[Log[x - 1] - 2 == 0,
x]}]
N[%]
Flatten[{NSolve[Log[x - 1] - 2 == 0, x], FindRoot[Log[x - 1] - 2 == 0,
{x, 10}]}]
Log[x - 1] - 2 == 0
(#1 + 2 & ) /@ %
Exp /@ %
Flatten[Solve[%, x]]
Out[14]=
{x -> 1 + E^2, x == 1 + E^2}
Out[15]=
{x -> 8.38905609893065, x == 8.38905609893065}
Out[16]=
{x -> 8.38905609893065, x -> 8.389056098930647}
Out[17]=
-2 + Log[-1 + x] == 0
Out[18]=
Log[-1 + x] == 2
Out[19]=
-1 + x == E^2
Out[20]=
{x -> 1 + E^2}
Dimitris
PS
In what y you are refered to?