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Author Comment/Response
Peter Pein
09/25/09 5:41pm

Hi Nick,

if you want exact expressions without "I", you could try ComplexExpand:

In[1]:= sol = TrigExpand[Solve[x^3 + x^2 - 8*x + 1 == 0,
x] /. (x -> r_) :> x -> ComplexExpand[r,
TargetFunctions -> {Abs, Arg}]]
Out[1]= {{x -> -(1/3) + (5/3)*
Cos[(1/3)*ArcTan[(3*Sqrt[5811])/101]] +
(5*Sin[(1/3)*ArcTan[(3*Sqrt[5811])/101]])/
Sqrt[3]},
{x -> -(1/3) + (5/3)*
Cos[(1/3)*ArcTan[(3*Sqrt[5811])/101]] -
(5*Sin[(1/3)*ArcTan[(3*Sqrt[5811])/101]])/
Sqrt[3]},
{x -> -(1/3) - (10/3)*
Cos[(1/3)*ArcTan[(3*Sqrt[5811])/101]]}}
In[2]:= N[x /. %]
Out[2]= {2.2954157235909167, 0.12728287906017538,
-3.4226986026510926}

Peter

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Subject (listing for 'Solving Polynomials')
Author Date Posted
Solving Polynomials Nick 09/19/09 4:58pm
Re: Solving Polynomials TomD 09/21/09 6:32pm
Re: Solving Polynomials yehuda ben-s... 09/22/09 08:31am
Re: Solving Polynomials Peter Pein 09/25/09 5:41pm
Re: Solving Polynomials Peter Pein 09/25/09 5:48pm
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