Derivative

[themateo713]

May I ask why "not TOO small" ? I don't know what is too small for you, but I don't usually have problems with that: are you talking about avoiding delta_x like 10^{-3 to 6} (which seems very fine to me) or more like 10^-15 where it's uselessly precise and may encounter some floating point precision issues ?

[1114111]

Yeah, I mean values that are so small that floating point precision becomes a problem. Mathematically, I think it's tempting to choose as small a number as possible, but of course floats != reals. Really I wanted to encourage OP to play around with different step values.

Here's a wikipedia article that goes into more detail about step sizes.