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 Author Comment/Response Forum Moderator email me 06/28/12 7:24pm Author later posted a longer version: ===== I have a set of coupled Differential Equations: \[Beta]'[t] == (Sqrt[3/2]*\[Alpha]^2*T[t]^(11/2))/m^(9/2)*(bb^2 - \[Beta][t]^2 T'[t] == (Sqrt[g]*T[t]^3)/(Sqrt[3]*M) with these conditions: M = 10000; g = 1; \[Alpha] = 1; A = 10; a = 0;(*initial plot temp*) b = .001; (*final plot temp*) c = .01; (*initial temp*) d = 0; (*initial \[Beta]*) m = .001; *Although the limits a and b can be manipulated to show the results best. What I want to do now not only solve this set of coupled differential equations but also generate a plot for \[Beta] as a function of T. I have B[t] and T[t] and what I want now is to generate a plot of B[t] from these equations. I have tried this; s = NDSolve[{\[Beta]'[t] == (Sqrt[3/2]*\[Alpha]^2*T[t]^(11/2))/m^( 9/2)*(bb^2 - \[Beta][t]^2), T'[t] == (Sqrt[g]*T[t]^3)/(Sqrt[3]*M), \[Beta][0] == 0, T[0] == c}, {\[Beta][t], T[t]}, {t, a, b}]; ParametricPlot[{(Evaluate[{T[t], \[Beta][t]} /. s])}, {t, a, b}, PlotRange -> Automatic] But I can't seem to generate anything coherent. Ideally this set of equations should regenerate the plots produced by: M = 10000; g = 1; \[Alpha] = 1; A = 10; a = .01;(*initial plot temp*) b = 1.2; (*final plot temp*) c = 0.00000001; (*initial temp*) d = 0; (*initial \[Beta]*) m = 1; bb = (g/(2*\[Pi])^(3/2)*(m/T)^(3/2)*E^(-m/T)); s = NDSolve[{\[Beta]'[T] == (3*\[Alpha]^2*M*T^(5/2))/( Sqrt[2*g]*m^(9/2))*(bb^2 - \[Beta][T]^2), \[Beta][c] == d}, \[Beta], {T, a, b}, Method -> "BDF"]; Plot[{(Evaluate[\[Beta][T] /. s])/bb}, {T, a, b}, PlotRange -> Automatic] Any and all help would be much appreciated!!! URL: ,

 Subject (listing for 'Solving Coupled Diff Eqs ( Simple )') Author Date Posted Solving Coupled Diff Eqs ( Simple ) William Duhe 06/27/12 11:55am Re: Solving Coupled Diff Eqs ( Simple ) Forum Modera... 06/28/12 7:24pm Re: Re: Solving Coupled Diff Eqs ( Simple ) Michael 06/30/12 6:09pm
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