Re: Problem with Solve and NSolve

*To*: mathgroup at smc.vnet.net*Subject*: [mg122449] Re: Problem with Solve and NSolve*From*: "David Park" <djmpark at comcast.net>*Date*: Sat, 29 Oct 2011 07:08:40 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <4981166.16368.1319792199648.JavaMail.root@m06>

There are an infinite number of roots so Mathematica can't give a solution. However, if you use an inequality to specify the x domain, Mathematica will find the solutions. The equation is even so one only needs the positive roots but I include the first few negative roots. Copy and evaluate the following in one cell. rootequation = x^3 Sin[x] == 1; Solve[{rootequation, -5 < x < 20}, x] % // N roots = x /. % For those who have the Presentations application the following will plot the roots on the curve and graduate the x axis using the root values. << Presentations` xticks = CustomTicks[Identity, databased[roots]]; Draw2D[ {Draw[x^3*Sin[x], {x, -5, 20}], Aliasing@Draw[1, {x, -5, 20}], CirclePoint[{#, 1}, 2, Black, ColorData["Crayola"]["TealBlue"]] & /@ roots}, AspectRatio -> 1/4, PlotRange -> {-10, 20}, Frame -> True, FrameTicks -> {{Automatic, Automatic}, {xticks, xticks // NoTickLabels}}, PlotLabel -> Style[phrase["Roots of ", rootequation], 16], ImageSize -> 600] David Park djmpark at comcast.net http://home.comcast.net/~djmpark/ From: V. Williams [mailto:gvicente at gmail.com] I've recently tried Mathematica 8.0.1, and I've found that it's unable to compute Solve[x^3*Sin[x]==1,x] (and the same with NSolve), which gives an error: Solve::nsmet: This system cannot be solved with the methods available to Solve WolframAlpha solves it without problems, so what's wrong with Mathematica?