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Re: How to find Complex roots !!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg26179] Re: How to find Complex roots !!
  • From: "A. Ciarkowski" <aciark at ippt.gov.pl>
  • Date: Thu, 30 Nov 2000 01:04:19 -0500 (EST)
  • References: <8uqumr$qp7@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Try this (here assumed n = 3 and a = 5):

g[x_] := x^3 + x^2

Solve[(g[x] + I f x - a /. f -> Normal[ Series[ Cos[x] + Cosh[x],
    {x, 0, 2} ]]) == 0, x ]

a=5;

Table[ FindRoot[ g[x] + I(Cos[x] + Cosh[x])x - a == 0,
    {x, %%[[i, 1, 2]]} ], {i, 3} ]

(* Verification: *)

g[x] + I(Cos[x] + Cosh[x])x - a /. %

Clear[a]

This can be simply adapted to a different n, by suitably
modifying g[x], and replacing {x, 0, 2} in the second command
by {x, 0, n-1}.

Adam


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