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Re: How do you input a solution from FindRoot into another equation?


In article <3mfauj$l4o at news0.cybernetics.net>, rdack at acs.ucalgary.ca (Robert Dack) writes:
|> 
|> Can someone tell me how to take the output from the FindRoot
|> cammand and input it into the next command line?  The output
|> comes out in the form { x -> 2.435 }, so the usual [%] command on
|> the next line won't work.
|> 
|> Any help in this area would be appriciated
|> 
|> R Dack   rdack at acs.ucalgary.ca
|> 
|> 
|> 
|> 
Sure.

The FindRoot command, returns a list as a solution.  In your case the list is
{x -> 2.435}.  You want to get at an element within that list, the root.  The 
Mathematica Part command allows you to do this.  Here's an example:

In[1]:=
FindRoot[Sin[x]==0,{x,3}]
Out[1]:=
{x -> 3.14159}
In[2]:=
%[[1]] 
Out[2]:=
x -> 3.14159
In[3]:=
%[[2]]
Out[3]:=
3.14159

You can combine the two steps into %[[1,2]] and get the same thing.


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