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 Author Comment/Response jf 03/31/12 5:55pm Note the "many" in the reference page for NDSolve, under More Information: "NDSolve can solve many differential-algebraic equations, in which some of the eqns are purely algebraic, or some of the variables are implicitly algebraic." The equation starting with Sqrt[z[t]] is algebraic. The warning message says the method NDSolve uses for differential-algebraic equations handles real values only. The equation starting with Sqrt[z[t]] is also wrong at t=0, since you get 0 == 339.583 I. Can you re-arrange the equations to have just differential equations? For example, Solve the algebraic equation for Z[t], take the derivative, and include that as a third differential equation in the system. references: http://reference.wolfram.com/mathematica/tutorial/NumericalSolutionOfDifferentialEquations.html http://reference.wolfram.com/mathematica/tutorial/NDSolveIDAMethod.html For backing up a calculation that is going the wrong way (like taking T[t] negative) see: http://www.wolfram.com/technology/guide/EventDetectionEventLocalization/ URL: ,

 Subject (listing for 'differential equations with conditions') Author Date Posted differential equations with conditions morrissey22 03/30/12 09:45am Re: differential equations with conditions jf 03/31/12 5:55pm
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