dx increment on WP 34s

[Richard Berler]

I was solving for f'(x) to find extremums of functions on my WP 34s. The default increment (which was arbitrary, but set by necessity) of .1 works well in most circumstances. I did find that there was something of a sweet spot around a dx of .029 in accuracy, and ability to solve f'(x) with an asymptote nearby. At dx=.1, the solve would find the asymptote too easily and show an infinity message. If I set the dx much below .029, the solve would slow down, lose accuracy, or fail on occasion.