Re: Periodic function Roots

*To*: mathgroup at smc.vnet.net*Subject*: [mg58403] Re: [mg58391] Periodic function Roots*From*: "David Park" <djmp at earthlink.net>*Date*: Fri, 1 Jul 2005 02:01:56 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

This is also a good example for using Ted Ersek's RootSearch package on MathSource. I believe he has just updated it, or is about to update it. The advantage is that it will find all the roots in a domain with a single command. Needs["Ersek`RootSearch`"] f[x_] := Cos[x] + .5 Cos[2x] + .25 Cos[3x] + 2.5 Cos[4x] RootSearch[f[x] == 0, {x, 0, 2\[Pi]}] {{x -> 0.51129}, {x -> 1.20136}, {x -> 1.91222}, {x -> 2.81887}, {x -> 3.46432}, {x -> 4.37096}, {x -> 5.08183}, {x -> 5.7719}} David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: FBellas [mailto:no at e.s] To: mathgroup at smc.vnet.net Hello, I'm trying to solve an periodic ecuation involving several harmonics (Style ACos(x)+BCos(2x)+...==K). Mathematica can't let me us 'Solve' function, so it gives me the error: Solve::tdep: The equations appear to involve the variables to be solved for \ in an essentially non-algebraic way. To arrange this, i'm making a little program involving FindRoot function to find at least two roots from the ecuation in the first period. But I would like to know if there are some other method to do this more easily. Thanks a lot F. Bellas