Mathematica NDSolve

  • #26
30,141
6,594
It looks like your equation does not involve any derivatives of \[CurlyPhi]i2p so it isn't an ordinary differential equation. It is a differential-algebraic equation, and it cannot solve all of those.
 
  • #27
17
0
Hi DaleSpam

Can you help me about the error findroot::istol please?
i recently used the code below but the error apeared :
------------------------------------------------------------------------------------------
lagrangesolveg2 =
NDSolve[{lagrangeq12 == 0, lagrangeq22 == 0, q1[0] == hh4,
q2[0] == hh5, q1'[0] == v1, q2'[0] == v2}, {q1, q2}, {t, 0, 1},
MaxSteps -> 1000000]
time2 = FindRoot[(q1[t] == -q2[t]) /. lagrangesolveg2, {t, 0.5, 0, 1}]

FindRoot::lstol: The line search decreased the step size to within tolerance specified by AccuracyGoal and PrecisionGoal but was unable to find a sufficient decrease in the merit function. You may need more than MachinePrecision digits of working precision to meet these tolerances. >>

{t -> 0.113944}
------------------------------------------------------------------------------------------
i really dont know what is the difference between AccuracyGoal and PrecisionGoal and their relativity to WorkingPrecision and MachinPrecision (even i read all of the helps in software guide). how can i get rid off the error?
 
  • #28
17
0
Sorry i should send you the complete code .forgot that you cant run without "lagrangeq"s &...
here is the full code as an attachment...
please help me as you done it well in the past, if possible...
 

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