Difeq in TI-85

To: CALC-TI@LISTS.PPP.TI.COM
Subject: Difeq in TI-85
From: Roland Bengtsson <roland-b@ALGONET.SE>
Date: Sun, 17 May 1998 21:52:11 +0100
Organization: Algonet/Tninet
Reply-To: Roland Bengtsson <roland-b@ALGONET.SE>
Xref: paladin.american.edu bit.listserv.calc-ti:23025

Is there a smart way to verify a solution for a difequation in TI-85?
Usual equations is no problem, just to exchange x with the answer but
difeqs seems to be harder...

How about this one:

y'' + 2y' + 5y = cos x

The answer should be:

      -x
y = (e  )(A cos (2x) + B sin (2x)) - 0.1 cos x + 0.2 sin x

Now I set y1=<the line above>

der2(y1,x) + 2 der(y1,x) + 5 y1

should be equal to cos x.
x happens to be 0.123 but this should not affect this.

It doesn't matter if I set A and B to 1, the values still differ.
Is there another way, send me a mail about it!


Thanks Roland

http://www.algonet.se/~roland-b

Follow-Ups:

Re: Visual verification of solution in DifEq mode in TI-85

From: Charles Reno <creno@en.com>

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