Re: der2 on TI-86?
[Prev][Next][Index][Thread]
Re: der2 on TI-86?
Michael Florea at michaelf@COLUMBIACU.ORG asked:
> Can anyone tell me why I can't do the following command on a TI-86?
>
> der2(x^3-12x^2+6x+10,x,0)
>
> This should just be the second derivative of the function at x=0 which
> equals -24, right? I keep getting "ERROR 04 DOMAIN". Am I missing
> something incredibly obvious?
I get the same result on my TI-86, and after further investigation I have
observed that on both the TI-85 and the -86:
der2(x^2,x,0) gives a domain error -- as does der1(x^1,x,0)
but, if you use the "x^2" key to produce the superscripted "2" for squaring:
der2(x[^2],x,0) works correctly -- as does der1(x,x,0)
Furthermore, there is no problem finding derivatives at points other than 0;
for example, der2(x^2,x,0.1) works correctly.
Note that der2(x^1.99999999,x,0) SHOULD (and does) give a domain error.
Perhaps the der2 algorithm incorrectly "sees" division by zero when taking
the second derivative of x^2 at 0, but does not have that problem when
squaring is done via the "x^2" key.
I'm too lazy to dig into this any further right now, but would be happy to
hear other insights or speculation.
--
Darryl K. Nester E-mail: mailto:nesterd@bluffton.edu
Assoc. Prof. of Mathematics WWW: http://www.bluffton.edu/~nesterd
Bluffton College Phone: 419-358-3483
Bluffton, OH 45817-1704 Fax: 419-358-3232
******************************************************************
* To UNSUBSCRIBE, send an email TO: listserv@lists.ppp.ti.com
* with a message (not the subject) that reads SIGNOFF CALC-TI
*
* Archives at http://peach.ease.lsoft.com/archives/calc-ti.html
******************************************************************
References: