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?