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Student Support Forum: 'I want to approximate a root of this equation' topicStudent Support Forum > General > Archives > "I want to approximate a root of this equation"

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Author Comment/Response
jf
03/13/13 12:42pm

Solve is happiest with polynomials. For a complicated equation, a numerical solver like FindRoot is more likely to work.

In[1]:= f[x__]:=(Sqrt[2] Sqrt[-E^(-2 p x) g R (-2-14 p^2-E^(2 p x) Cos[x]+2 E^(2 p x) p^2 Cos[x]+3 E^(2 p x) p Sin[x])])/Sqrt[1+4 p^2]

In[2]:= g=10;
R=2;
p=0.3;

In[5]:= FindRoot[ f[x]^2==-g R Cos[x], {x,1}]
Out[5]= {x->1.74393}

This takes the Rule that FindRoot gives and uses it to substitute the value for the x's:

In[6]:= f[x]^2==-g R Cos[x] /. %
Out[6]= True


FindRoot is included in the See Also in the reference page for Solve and in
http://reference.wolfram.com/mathematica/tutorial/SolvingEquations.html



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Subject (listing for 'I want to approximate a root of this equation')
Author Date Posted
I want to approximate a root of this equation Joćo Maldonado 03/13/13 12:04pm
Re: I want to approximate a root of this equation jf 03/13/13 12:42pm
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