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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?
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