Re: Solve fails
- To: mathgroup at smc.vnet.net
- Subject: [mg33331] Re: [mg33326] Solve fails
- From: BobHanlon at aol.com
- Date: Sat, 16 Mar 2002 01:40:08 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
In a message dated 3/14/02 8:11:32 PM, fateman at cs.berkeley.edu writes:
>Solve[x*Sin[x]==x*Sin[x^3],x] gives {{}}
>
>but
>Solve[Sin[x]==Sin[x^3],x] returns unchanged
>
>each gives a warning.
>
>There are very many solutions, among them x=0, x=+-1,
>x=+-2.0253909752730426 approximately
>
"Solve deals primarily with linear and polynomial equations."
NSolve[x*Sin[x]-x*Sin[x^3],x]
Solve::ifun: Inverse functions are being used by Solve, so some solutions may
not be found.
{{x -> 0.}}
Use FindRoot
Plot[x*Sin[x]-x*Sin[x^3], {x,-2.5,2.5}];
Union[
Select[
Flatten[
Table[
FindRoot[x*Sin[x]==x*Sin[x^3],{x,k},
AccuracyGoal->12, WorkingPrecision->22,
MaxIterations->50],
{k,-2.5,2.5,.1}]],
Abs[#[[2]]]<= 2.5&],
SameTest->(Abs[#1[[2]]-#2[[2]]]<(10^-6)&)]
Length[%]==13
Bob Hanlon
Chantilly, VA USA