Derivatives on HP 42S

[Albert Chan]

(08-26-2018 04:47 PM)lrdheat Wrote:  When I run dx for, say, pi/4 (let's be simple and use fx=sin x), I get ~0 instead of ~.707

my guess is you forget to divide by h:

df(x) ~ Im((f(x + i*h)) / h

Code:

>>> from cmath import *
>>> h = 1e-6
>>> sin(complex(pi/4, h).imag
7.0710678118666542e-07
>>> _ / h
0.70710678118666548