#8931: desolve fails when assumptions required
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Reporter: descopau | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-4.5.3
Component: symbolics | Keywords: desolve
Author: G.Connan | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Comment(by monkey):
I have the same problem solving a different equation:
{{{
var('L1 L2 C1 C2 L3 C3 t')
forget()
assume(L2 > 0)
assume(L3 > 0)
assume(C2 > 0)
assume(C3 > 0)
j = function('j',t)
eqn = diff(v_i,t) - L2*diff(j,t,2) - j/C2 == L3*diff(j,t,2) + j/C3
desolve(eqn,[j,t],[0,1])
}}}
returns
{{{
Traceback (click to the left of this block for traceback)
...
Is C2*C3*(C3+C2)*(L3+L2) positive, negative, or zero?
}}}
The only quick workaround I have found is to specify the values of the
constants, but I really need them to be symbolic. The best I can do is
use primes for values of constants and after several such sets you can get
a picture of how the constants are related to the numbers in the solution
terms, but it's an ass-ache.
I think the best solution would be to have an optional argument to desolve
which answers the question posed if there are not sufficient
assumptions/conditions to already determine the correct answer.
Really appreciate the great work so far guys! :D
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8931#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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