Re: How can I find roots in Mathematica 6?

• To: mathgroup at smc.vnet.net
• Subject: [mg83585] Re: [mg83517] How can I find roots in Mathematica 6?
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Fri, 23 Nov 2007 05:39:44 -0500 (EST)

soln = Reduce[{Cosh[z]  ==  I,  Abs[Im[z]]  < 10},  z]

z == -2*I*Pi - ArcCosh[I] ||
z == 2*I*Pi - ArcCosh[I] ||
z == -ArcCosh[I] ||
z == ArcCosh[I] ||
z == -2*I*Pi + ArcCosh[I] ||
z == 2*I*Pi + ArcCosh[I]

soln // N

z == -0.8813735870195429 -
7.853981633974483*I ||
z == -0.8813735870195429 +
4.71238898038469*I ||
z == -0.8813735870195429 -
1.5707963267948966*I ||
z == 0.8813735870195429 +
1.5707963267948966*I ||
z == 0.8813735870195429 -
4.71238898038469*I ||
z == 0.8813735870195429 +
7.853981633974483*I

Cosh[Last /@ List @@ soln]

{I, I, I, I, I, I}

Bob Hanlon

---- DrunkenButterfly <darkladymacbeth at hotmail.com> wrote:
> Does anyone know what should I type in in order to find the roots of
>
> cosh(z)=i with Abs[Im[z]]<10    ?
>
> I've just started using Mathematica 6 and the help browser is not really helping me at all. Thanks!
>

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