ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Sat, 29 Nov 2014 05:42:52 +0100Why does Sage not find any solutions using .solve()?https://ask.sagemath.org/question/24991/why-does-sage-not-find-any-solutions-using-solve/ Hello everyone,
please consider this attempt to solve simultaneous equations:
P,M,R,rho,kappa,T,F,n = var('P, M, R, rho, kappa, T, F, n')
eqns = [
P==M^2*R^-4,
R^3==M*rho^-1,
T^4==M*kappa*F*R^-4,
F==M*rho*T^n,
P==rho*T,
kappa==rho*T^(-7/2),
n==4
]
eqns
assume(P>0,M>0,R>0,rho>0,T>0,F>0,kappa>0)
sols = solve(eqns,(F,R,T))
sols
(returns [])
I would like to understand why Sage can not arrive at a relation for F,M,T (and n) which I was able to do by hand. Is solve inappropriate for isolating one or more variables from a set of equations?
Thank you for your help!
Tue, 25 Nov 2014 12:56:59 +0100https://ask.sagemath.org/question/24991/why-does-sage-not-find-any-solutions-using-solve/Comment by FrédéricC for <p>Hello everyone,</p>
<p>please consider this attempt to solve simultaneous equations:</p>
<pre><code>P,M,R,rho,kappa,T,F,n = var('P, M, R, rho, kappa, T, F, n')
eqns = [
P==M^2*R^-4,
R^3==M*rho^-1,
T^4==M*kappa*F*R^-4,
F==M*rho*T^n,
P==rho*T,
kappa==rho*T^(-7/2),
n==4
]
eqns
assume(P>0,M>0,R>0,rho>0,T>0,F>0,kappa>0)
sols = solve(eqns,(F,R,T))
sols
</code></pre>
<p>(returns [])</p>
<p>I would like to understand why Sage can not arrive at a relation for F,M,T (and n) which I was able to do by hand. Is solve inappropriate for isolating one or more variables from a set of equations?</p>
<p>Thank you for your help!</p>
https://ask.sagemath.org/question/24991/why-does-sage-not-find-any-solutions-using-solve/?comment=25006#post-id-25006something close works
sage: solve(eqns, (F,R))
[kappa == rho/T^(7/2), n == 4, F == M*T^n*rho, P == M^2/R^4, P == T*rho, R^3 == M/rho, T^4 == F*M*kappa/R^4]Tue, 25 Nov 2014 21:59:54 +0100https://ask.sagemath.org/question/24991/why-does-sage-not-find-any-solutions-using-solve/?comment=25006#post-id-25006Comment by tmonteil for <p>Hello everyone,</p>
<p>please consider this attempt to solve simultaneous equations:</p>
<pre><code>P,M,R,rho,kappa,T,F,n = var('P, M, R, rho, kappa, T, F, n')
eqns = [
P==M^2*R^-4,
R^3==M*rho^-1,
T^4==M*kappa*F*R^-4,
F==M*rho*T^n,
P==rho*T,
kappa==rho*T^(-7/2),
n==4
]
eqns
assume(P>0,M>0,R>0,rho>0,T>0,F>0,kappa>0)
sols = solve(eqns,(F,R,T))
sols
</code></pre>
<p>(returns [])</p>
<p>I would like to understand why Sage can not arrive at a relation for F,M,T (and n) which I was able to do by hand. Is solve inappropriate for isolating one or more variables from a set of equations?</p>
<p>Thank you for your help!</p>
https://ask.sagemath.org/question/24991/why-does-sage-not-find-any-solutions-using-solve/?comment=25050#post-id-25050Well, the solution is only a copy/paste of the equations (which i agree is equivalent, so at least there is no lie), no variable isolation happened.Sat, 29 Nov 2014 05:42:52 +0100https://ask.sagemath.org/question/24991/why-does-sage-not-find-any-solutions-using-solve/?comment=25050#post-id-25050