I want to plot E with respect to t.
I typed the sys of this equation and try to plot it with DEplot but failed.
This is the code
DEplot([sys], [x(t), y(t), E(t)], t = -25 .. 25, [[x(0) = -.3, y(0) = .2]], scene = [E(t), t], stepsize = 0.5e-1, linecolor = red, arrows = none);
The error is Error, (in DEtools/DEplot/CheckDE) derivatives must be given explicitly.
Eager to know the answer, please help me . Thanks very much.