(41C) Area of Triangle (SSS)

[Dieter]

(11-12-2018 02:55 PM)Albert Chan Wrote:  

(11-10-2018 03:22 PM)Albert Chan Wrote:  If the sides are sorted, a >= b >= c, Kahan's formula is more accurate.

(11-12-2018 01:32 AM)Albert Chan Wrote:  Let y = (c - (a-b))*(c + (a-b)) / 4, then Area Δ = √((ab-y)*y)

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Edit: this is the HP-12C code for above tests (order does not matter):

Both the formula and the program look good.
But is there a proof that the formula is (at least) as exact as Kahan's?
Testing some examples does not count. ;-)

Dieter