Re: General--Differential equation problem..

*To*: mathgroup at smc.vnet.net*Subject*: [mg66302] Re: [mg66284] General--Differential equation problem..*From*: Bob Hanlon <hanlonr at cox.net>*Date*: Mon, 8 May 2006 00:46:54 -0400 (EDT)*Reply-to*: hanlonr at cox.net*Sender*: owner-wri-mathgroup at wolfram.com

Clear[z]; With[{r=2},z=z/.DSolve[{z'[s] == 1/r,z[0]==0},z, s][[1]]]; Clear[x,y]; {x,y}={x,y}/.DSolve[ {x'[s]==Cos[z[s]], y'[s]==Sin[z[s]],x[0]==0,y[0]==0}, {x, y}, s][[1]]; {x[s],y[s],z[s]} {2*Sin[s/2], -2*(Cos[s/2] - 1), s/2} With[{r=2},{x'[s] == Cos[z[s]], y'[s] == Sin[z[s]], z'[s] == 1/r}] {True,True,True} Table[ParametricPlot[{x[s], y[s]}, {s, 0, smax}, PlotRange->{{-2.1,2.1},{-0.1,4.1}},Frame->True,Axes->False], {smax,Pi/6,4Pi,Pi/6}]; Bob Hanlon ---- randomtalk at gmail.com wrote: > hello, i was trying to solve a set of differential equations needed for a school project.. However, i'm completely new to mathematica 5.0, and i have downloaded trial, here is what i inputed into the software: > > In[2]:= > DSolve[{x'[s] == Cos[z], y'[s] == Sin[z], z'[s] == 1/r, r == 2}, {x, y, z}, s] > > returns this error: DSolve::dvnoarg: The function z appears with no arguments. > > Is there anything wrong with what i inputed? The differential equations came from this website: http://fy.chalmers.se/LISEBERG/eng/loop_pe.html > > Link to the forum page for this post: > http://www.mathematica-users.org/webMathematica/wiki/wiki.jsp?pageName=Special:Forum_ViewTopic&pid=10212#p10212 > Posted through http://www.mathematica-users.org [[postId=10212]] > >