Subject: implicit diff & subst problems... /just to you.
From: Evan Cooch
Date: Thu, 06 Oct 2011 14:36:15 -0400
Indeed -- so I finally figured out, with the help of many replies to my
original query.
Thanks!
On 10/6/2011 1:00 PM, dlakelan wrote:
> On 10/06/2011 09:02 AM, Evan Cooch wrote:
>
>> Now, an earlier answer gave me a clue as to how to accomplish this in
>> Maxima -- it looks (to me) like when I execute the following
>>
>>
>> --> mat:matrix([0,s_a*m_2,s_a*m_3],[s_o,0,0],[0,s_a,0]);
>> --> cp:charpoly(mat,lambda);
>> --> depends(lambda,s_a);
>> --> deriv:diff(cp,s_a);
>> --> sol:solve(deriv,'diff(lambda,s_a));
>>
>>
>> then what Maxima returns for sol is a vector, or some similar construct,
>> where there is importance to the the LHS and RHS (which appear to be
>> separately addressable), and that to use subst, you need to tell it to
>> look/focus on the RHS, and ignore the LHS, where the LHS indicates that
>> it is a derivative, which is true, but irrelevant to the purpose of
>> numerically evaluating the function.
> Maxima is giving you an equation (actually a list of equations, in case
> there might be more than one solution), every equation has a left and a
> right hand side. In this case, the left hand side tells you what was
> solved for, and the right hand side tells you the solution. If you
> substitute into the equation you will be substituting into both sides.
> That is why you must take the right hand side before using subst to
> evaluate.
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