Re: how do I solve for this
- To: mathgroup at smc.vnet.net
- Subject: [mg117637] Re: how do I solve for this
- From: Peter Breitfeld <phbrf at t-online.de>
- Date: Tue, 29 Mar 2011 06:51:20 -0500 (EST)
- References: <imfa6a$io5$1@smc.vnet.net>
thinktank1985 wrote:
First make your variables constant (I use n instead of N, because N is a
function, which should not be used as a Variable):
SetAttributes[{p,n,kb,b,a},Constant]
your equation:
eq = p == (n kb T)/(V - n b) - (a n^2)/V^2
Calculate the total derivative:
totDiff=Dt[eq,T]
Out=
0 == (kb n)/(-b n + V) + (2 a n^2 Dt[V, T])/V^3 -
(kb n T Dt[V, T])/(-b n + V)^2
Solve for Dt[V,T]:
Solve[totDiff,Dt[V,T]] // Together
Out= {{Dt[V, T] -> (kb n (b n - V) V^3)/
(2 a b^2 n^4 - 4 a b n^3 V + 2 a n^2 V^2 - kb n T V^3)}}
> Say I have
>
> p=N*kb*T/(V-N*b)-a*N^2/V^2
>
> I want to evaluate the derivative of V with respect to T, keeping
> p,N,kb,b,a constant.
>
> I understand that this can be done by hand. I just want to know
> whether this can be done by using mathematica. I couldnt understand
> how to use Solve to do this. maybe there is something else I am not
> aware of
>
--
_________________________________________________________________
Peter Breitfeld, Bad Saulgau, Germany -- http://www.pBreitfeld.de