Casio FX-115MS bug
11-07-2018, 10:47 PM (This post was last modified: 11-21-2018 01:04 PM by Albert Chan.)
Post: #9
 Albert Chan Senior Member Posts: 1,985 Joined: Jul 2018
RE: Casio FX-115MS bug
Hi, klesl

I don't expect exact result. But the result seems not due to rounding errors.
Relative errors of 0.003% is not the upper bound. Try this:

X³ + 11 X - 1000100 = 0

Cubic Solver still returned real root of 100.0033332

For above cubic, u is still about 100.0033332, but r is now 11/3

X = u - r/u = 99.96666778, so Solver result only have 3 good digits.

If it is a generalized solver, maybe 3 or 4 good digits is enough.
But, this is a specialized Cubic Solver, with known formula for it.

Even worse case may be possible (example, by adding X² term)

Update: Let Y = X - 100, hoping for better luck:

Y³ + 300 Y² + 30011 Y + 1000 = 0

Expecting Y correction of -0.03333222. Instead, I got +0.003333223
Cubic Solver get the sign wrong ! (Relative error of 110% !)
 « Next Oldest | Next Newest »

 Messages In This Thread Casio FX-115MS bug - Albert Chan - 10-31-2018, 07:02 PM RE: Casio FX-115MS bug - klesl - 11-01-2018, 11:14 AM RE: Casio FX-115MS bug - ijabbott - 11-01-2018, 08:16 PM RE: Casio FX-115MS bug - G. Cook - 11-02-2018, 09:14 PM RE: Casio FX-115MS bug - Albert Chan - 11-03-2018, 02:41 PM RE: Casio FX-115MS bug - Albert Chan - 11-05-2018, 08:58 PM RE: Casio FX-115MS bug - Albert Chan - 11-07-2018, 08:15 PM RE: Casio FX-115MS bug - Albert Chan - 11-07-2018 10:47 PM RE: Casio FX-115MS bug - Albert Chan - 11-08-2018, 04:17 PM RE: Casio FX-115MS bug - Albert Chan - 11-24-2018, 07:25 PM RE: Casio FX-115MS bug - ijabbott - 11-24-2018, 08:28 PM RE: Casio FX-115MS bug - klesl - 11-07-2018, 08:33 PM RE: Casio FX-115MS bug - Albert Chan - 11-08-2018, 02:51 PM RE: Casio FX-115MS bug - brickviking - 11-28-2018, 01:01 AM

User(s) browsing this thread: 1 Guest(s)