deSolve Error

[Luke Setzer]

I can enter

deSolve(0.01*v'+0.0025*v=0,t,v)

and get

v=1*^(((−t)/(4)))

as a general solution.

But when I enter

deSolve(0.01*v'+0.0025*v=0 and v(0)=100,t,v)

I get

"Error: Argument must be a variable name."

I cannot for the life of me see what I have entered wrongly.

Can someone please help?

[Andy Kemp]

Strange one this, it seems it doesn't like the order of your ODE.  If you rewrite it as:

deSolve(0.01*v'=−0.0025*v and v(0)=100,t,v)

Then it solves it quite happily...

I can't see any reason why though, my guess would be this is a bug...

--
To post to this group, send email to tins...@googlegroups.com
To unsubscribe send email to tinspire+u...@googlegroups.com
For more options, visit this group at
http://groups.google.com.au/group/tinspire?hl=en-GB?hl=en-GB
The tns documents shared by group members are archived at
http://lafacroft.com/archive/nspire.php

[Luke Setzer]

Thanks, Andy! Does TI Technical Support read this forum? I hope
those in power fix the bug!

>  11-04-2011 Image011.jpg
> 23KViewDownload

[Andy Kemp]

I am quite sure they are paying attention!

[Wayne]

Luke,

Are you using Version 3.0 or an earlier version of the OS? I only
have 3.0 installed now and I certainly see the same behavior.
However, I believe that Version 2.1 would have correctly handled this
problem. Could someone who still has OS 2.1 check to see how it
handles this problem? I am guessing this is a new problem in OS 3.0.

Wayne

> > 23KViewDownload- Hide quoted text -
>
> - Show quoted text -

[Nelson Sousa]

2.1 has no problem with it.

Cheers,
Nelson

[Luke Setzer]

I "upgraded" to 3.0 before working this problem so apparently the
"upgrade" has slightly "downgraded" performance of the deSolve feature!

[Daniel Tran]

please email Ti about this

[Wayne]

FWIW, OS 3.0 also has problems with some second order homogeneous DE's
with initial conditions, e.g.,
desolve(y''+1/100y'+1/10000y=0 and y(0)=0 and y'(0)=1,t,y) returns
that same error. If the equation is entered with the highest order
derivativve alone on the left-hand-side of the equation and lower
order derivative terms on the right-hand-side, then OS 3.0 seems to
handle that format without problems, so that could be a workaround
until TI can check out the problem. As far as reporting the error,
some of the well-connected posters have assured us that TI monitors
this forum and that the developers will see the thread. I guess that
is enough for now?

Wayne

On 12 Apr, 09:54, Daniel Tran <tutran...@gmail.com> wrote:
> please email Ti about this

[Luke Setzer]

I received a private message from TI saying they are aware of the
problem, that it arose as a result of the new completeSquare()
functionality, and that they intend to fix it whenever they release
the next upgrade.

[Sean Bird]

I have no idea when another release will be out, but historically speaking (i.e. last year) there has been an update before school started. (E.g. 2.0 came out in the spring and teachers could decide if they wanted to upgrade then or wait for the summer. Then 2.1 was released before school started.)

[Joe]

So I take it that if I buy the new nspire cx cas when it becomes
available in a few weeks, it will have a deSolve function that doesn't
won't work correctly if the calc uses OS 3.0? I don't want that and
in view of the problems people are having updating the OS I don't want
to go thru that either. Does anyone know of a supplier who will tell
you me OS version I will get when purchasing a calc? Like is it
indicated somewhere on the container or paperwork?

On Apr 12, 9:29 am, Sean Bird <covenantb...@gmail.com> wrote:
> I have no idea when another release will be out, but historically speaking
> (i.e. last year) there has been an update before school started. (E.g. 2.0
> came out in the spring and teachers could decide if they wanted to upgrade
> then or wait for the summer. Then 2.1 was released before school started.)
>

> On Tue, Apr 12, 2011 at 11:29 AM, Luke Setzer <LutherSet...@yahoo.com>wrote:
>
>
>
> > I received a private message from TI saying they are aware of the
> > problem, that it arose as a result of the new completeSquare()
> > functionality, and that they intend to fix it whenever they release

> > the next upgrade.- Hide quoted text -

[Jessica Kachur]

The cx will come with 3.0 no matter what.  You need 3.0 to use the CX.  I think the role out of the new OS had a few glitches, but I think it is better.  Also, you wont have to get a new os until the new one comes out in 6 - 12 months or so.
 

Jess Kachur
T3 Regional Instructor
Muka, CGC, TDI, Retired, CL2, CL3-F, CL3-S, CL3-H, TN-O, WV-N
and
Jibay, Sandy Acres lil' Phantom, NA, CGC, CL4, CL4-F, CL4-S, CL4-H

---

From: Joe <wjb...@yahoo.com>
To: tinspire <tins...@googlegroups.com>
Sent: Tue, April 12, 2011 8:18:42 PM
Subject: [tinspire] Re: deSolve Error

--
To post to this group, send email to tins...@googlegroups.com

To unsubscribe send email to tinspire+unsub...@googlegroups.com

[Nelson Sousa]

All CX will have 3.0. But no, the os version is not visible on the packaging. If you don't want to upgrade to 3.0 you should stick to the touchpad Nspire until 3.1 is released.

--
Nelson

[Bikash Jain]

Are we expecting another update in software?

Regards-

Bikash Jain

[Andy Kemp]

Only in the sense that since TI released the Nspire there has been an update roughly every 6 months...

[Jimmy Fullerenex]

For the deSolve error, I've found that if you first enter the expression as a string, say, str:="0.01y'+0.0025y=0 and y(1)=0" then use expr(), the system will process happily:

deSolve(expr(str),t,y)

My further suggestion is that we may write a function, and while we input, we use some combinations of letters to replace the prime (I assume that you already have the replace() func):

desolve2(str,var1,var2):=Func

deSolve(expr(replace(string(str),"ab"," ' ")),var1,var2)          where we use "ab" to denote the prime

EndFunc

So now we get

desolve2(0.01yabab+0.03yab+0.0025y=0 and y(1)=0 and yab(2)=1,t,y)
--

Cheers,

Jimmy Fullerenex

[Joe]

Thanks to eveyone for the information. I appreciate very much the
guidance. If I had purchased the new cx cas only to find out that I
was sold a product that had a known flaw in it I would have been
furious.

THE FOLLOWING MESSAGE IS FOR TI: I want you (TI) to know that I've
carefully thought over the possibility of deSolve not working properly
on a cx cas that I might buy and I have come to the following
conclusions. Yes, I was going to buy your new cx cas as soon as it
became available, but no I am not going to buy that product if it
needs to be fixed by a later OS update which may or may not occur at
some unspecified date. Hopefully you are taking corrective action and
I don't need to point this out but just to be clear, you need to take
the time and fix this quality problem and not ship calculators that
you know don't work properly. It is my opinion that you have a moral
obligation to do that and if you cannot or won't do that then you do
not deserve my business or anyone elses for that matter. I work hard
for my money and I am not about to waste it on products that are known
to not work properly. If you wish to reply you can do so here or use
the "Reply to author option." Thank you.

> >http://lafacroft.com/archive/nspire.php- Hide quoted text -