Thanks Hartmut for the HP-15C test.
It seems HP-15C does *decimal* math, 10 significant digits, half-round-up
s = (a + b + c) / 2
= (1e5 + 99999.99979 + 0.00029) / 2
= (199999.9998 + 0.00029) / 2 -- round up
= 200000.0001 / 2 -- round up again
= 100000.0001 -- half-round-up
I have never seen a calculator like this ...
With this, I match your area result of 17.60681685 exactly.
On Jun 12, 2018, at 5:38 PM, Hartmut Henkel <firstname.lastname@example.org> wrote:
On Tue, 12 Jun 2018, Albert Chan wrote:BTW, the article stated that heron formula return area = 17.6I cannot reproduce it (even adjusting precision with gmpy2)Anyone still have the old HP-15C calculator ?