[WP-34S] DEG and RAD - diffs

[Claudio L.]

(06-06-2014 01:51 AM)Paul Dale Wrote:  

(06-06-2014 01:31 AM)Claudio L. Wrote:  There's other cases where this can't be avoided: cosh() for example.

Cosh is easily worked out from the definition: (e^x + e^-x)/2.
For x large (positive or negative), one term dominates. For x small, there are both relevant but of similar magnitude.

Sinh is a completely different beast.


- Pauli

Yeah, I made a mistake, it was acosh() not cosh the one that gave me trouble (the rotation mode in CORDIC is quite stable, vectoring mode is much worse), since the argument close to 1 leaves you very few significant digits to work with.
Also ln() is very tricky (it's also in rotation mode), because the input to the CORDIC algorithm is (1-x) and (1+x). When x is close to one you lose a lot of digits in the first one, and when it's close to zero you lose them in the other one. Can't win.

Claudio