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Re: What am I doing wrong with this code?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg82535] Re: What am I doing wrong with this code?
  • From: Peter Pein <petsie at dordos.net>
  • Date: Wed, 24 Oct 2007 04:23:11 -0400 (EDT)
  • References: <ffkffr$spa$1@smc.vnet.net>

sean_incali schrieb:
> I think I'm having a brain fart. Seriously...
> 
> Plot[{1/(1 + y^2), (1/y - 1)^(1/2)}, {y,  0, 5}]
> 
> What is wrong with that code? Maybe it's not solvable in mathematica?
> 
> I'm trying to plot nullclines of a system of ODEs. and those function
> up there are them. I just can't get mathematica to plot them in the
> same graph.
> 
> I get an error message saying...
> 
>>From In[22]:=
> (1/y - 1)^(1/2)  is not a machine-size real number at y =
> 1.0000001666666667`.
> 
> Any help is appreciated.
> 
> sean
> 
> 

The complex numbers are _not_ a subset of the real numbers:
In[1]:=
(1/y - 1)^(1/2) /.
  y -> 1.0000001666666667
Out[1]=
0. + 0.00040824825649889477*I

... and air your room ;-)


Peter


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