Re: General--Differential equation problem..

*To*: mathgroup at smc.vnet.net*Subject*: [mg66295] Re: General--Differential equation problem..*From*: "Stratocaster" <stotz1 at verizon.net>*Date*: Mon, 8 May 2006 00:46:27 -0400 (EDT)*References*: <e3jttb$94n$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

<randomtalk at gmail.com> wrote in message news:e3jttb$94n$1 at smc.vnet.net... > 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] I'm not sure how new you are to Mathematica, so please don't take offense if this is common knowledge to you. You didn't type the In[2]:= Right? If you did then don't, if you didn't then great (sorry to have doubted you)! > returns this error: DSolve::dvnoarg: The function z appears with no > arguments. And it is doing this because you have declared z a function within the DSolve statement. DSolve[{These Differential Equations},{for these functions of s}, with independent variable s]. > Is there anything wrong with what i inputed? Yes. The function z appears with no arguments. Try using this: DSolve[{x'[s] == Cos[z[s]], y'[s] == Sin[z[s]], z'[s] == 1/2}, {x[s], y[s], z[s]}, s] You see Cos[z[s]]? z makes no sense if you are solving for z[s]. Notice also that for the second argument I used {x[s],y[s],z[s] }? I also removed the "r == 2" and just plugged "2" for the equation regarding z[s]. Did this give you what you needed?