Re: Derivative on 35s Message #4 Posted by Peter Niessen on 23 Aug 2007, 5:23 p.m., in response to message #2 by Peter Niessen
Try solving for the root of, e.g. (x2)^2+1:
LBL F
RCL X
2

x^2
1+
RTN
then
FN=F
SOLVE X
will give you "NO ROOT FOUND", but a 2 in the display.
Of course, as soon as your function has a root, this method will not work.
You probably could do (limited) symbolic derivatives using RPN, using the indirect array, since differentiating in RPN is easier than in ALG:
e.g. x^2
X x^2
can be diff'd by replacing x^2 by 2 *.
Addition and subtraction just stays the same (+ and ).
Product rule is a bit more advanced: You have to replace
X Y *
by
X Y' * X' Y * +
and have to evaluate X', Y' by recursion.
All what's left is to find a suitable representation of the symbols as numbers in the indirect registers, but that's a triviality :)
Cheers, Peter.
Edited: 23 Aug 2007, 5:24 p.m.
