bugGNU Octave - Bugs: bug #60239, [octave forge] (symbolic)...

 
 

bug #60239: [octave forge] (symbolic) Differential equations with initial conditions sometimes return wrong result

Submitted by:  None
Submitted on:  Mon 15 Mar 2021 07:02:51 PM UTC  
 
Category:  Octave Forge Package Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  None Assigned to:  None
Originator Name:  Originator Email:  -email is unavailable-
Open/Closed:  Open Release:  6.2.0
Operating System:  Any

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Sun 21 Mar 2021 08:00:38 AM UTC, comment #2: 

This issue is coming from sympy.

Anonymous
Mon 15 Mar 2021 07:07:50 PM UTC, comment #1: 

syms y1(x) y2(x) M

Anonymous
Mon 15 Mar 2021 07:02:51 PM UTC, original submission:  

syms y1 y2 M

DE1 = diff(diff(y1)) == -2*y1+y2
DE2 = diff(diff(y2)) == -2*y2+y1

DE = [DE1 DE2]
s = dsolve(DE,diff(y1)(0)==0,diff(y2)(0)==0,y1(0)==M,y2(0)==-M)
s{1}

// constant C_4 is not replaced by M/2
// the correct result is that C_4 = C_3
// s{1} is expected to be shown as M*cos(sqrt(3)*x)

Anonymous

 

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    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2021-03-16 siko1056 CategoryOctave Function => Octave Forge Package
        SummaryDifferential equations with initial conditions sometimes return wrong result => [octave forge] (symbolic) Differential equations with initial conditions sometimes return wrong result

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