Try this
ClearAll[eqn, ics, ode]
eqn = x''[t] + 20.*x'[t] + 30.*x[t] == 35.*Sin[2.*Pi*2.*t]
ics = {x[0] == 0., x'[0] == 0.}
ode = Flatten[{eqn, ics}]
ClearAll[sol];
sol = NDSolve[ode, x, {t, 0, 5.}, AccuracyGoal -> 14, PrecisionGoal -> 14][[1]]
Plot[Evaluate[eqn /. sol], {t, 0, 5.}]
The Plot command yields empty plot in Mathematica 10, but in 9.0.1 and 8.0.4 a plot results.
I often have many differential equations I would like to plot to see the effects of Accuracy and Precision goals and the above is a simple, rough way to do it.
Even this no longer works in Mathematica 10, but does in 9.0.1 and 8.0.4:
Plot[Evaluate[2 x^2 + 3 x == 20], {x, -5, 5}]
It seems a bit burdensome to do
Plot[Evaluate[eqn[[1]] - eqn[[2]] /. sol], {t, 0, 5.}, PlotRange -> All]
especially if I have quite a few differential equations.
Suggestions welcome unless this is unintended behavior, then Wolfram guys please let me know.
Notebook attached.
-B
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