First I define the 5th order derivative of my function of t to be sin(t):
f = Sin[t];
tMax = Pi/2;
nds = NDSolve[{
x'''''[t] == f,
x''''[0] == 0,
x'''[0] == 0,
x''[0] == 0,
x'[0] == 0,
x[0] == 0
}, x, {t, 0, tMax},
MaxSteps -> Infinity];
Then I make up the Plotting command:
plot[?_] :=
Plot[Evaluate[? /. nds], {t, 0, tMax}, Frame -> True,
PlotRange -> All]
xt = Evaluate[x[tMax] /. nds][[1]] "m"; "x(t)" -> xt
plot[x[t]]
ct = Evaluate[x'''''[tMax] /. nds][[
1]] "m/sec^5"; "c(t)" -> ct
plot[x'''''[t]]
?his works well up to the 3rd detivative, but at the 4th and 5th it starts oscillating like crazy. The function of the 5th derivative should be a plain Sinus, but it looks like this:
http://s24.postimg.org/6wifn1gx1/5thderivative.png
When I define lower derivatives the expected function always comes out clearly, but it always starts breaking down at order 4 or 5. I tried to increase WorkingPrecision, but that only made it worse. Any ideas?
Scratching my head,
Yukterez
PS: I work on Mathematica 9, because version 10 was unstable in various ways. If this problem does not appear in version 10 please tell me, then I will reinstall it.
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