[Emulator] Laplace Transform Question

[Emulator] Laplace Transform Question - Printable Version

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[Emulator] Laplace Transform Question - thescreensavers - 05-30-2014 12:17 AM

[Image: srKqOAI.png]

Im inputting laplace( te^(-3t) sin(5t))

Wolfram Gets [Image: ziVoC17.gif]

Emulator Spits out

[Image: okxlhXi.png]

What am I doing wrong?

RE: [Emulator] Laplace Transform Question - parisse - 05-30-2014 06:41 AM

the variable t and s are missing:
laplace(t*exp(-3t)*sin(3t),t,s)
With 1 argument the variable must be x: laplace(x*exp(-3x)*sin(3x))

RE: [Emulator] Laplace Transform Question - Maro - 05-30-2014 07:52 AM

I didn't try the emulator, but on the hardware Laplace Transform always results in a message "Unable to check if antiderivative ….", no matter which variables / parameters are used. Seems to be a new software bug.

After pressing ENTER again, the transformation result shows up.

I didn't see that before the new firmware update. However, before the update some transformations did not work at all.

RE: [Emulator] Laplace Transform Question - thescreensavers - 05-30-2014 02:41 PM

(05-30-2014 06:41 AM)parisse Wrote: the variable t and s are missing:
laplace(t*exp(-3t)*sin(3t),t,s)
With 1 argument the variable must be x: laplace(x*exp(-3x)*sin(3x))

That makes sense.

ok so I put it in CAS mode I copied and pasted what you wrote(fixed the 3t for sin to 5t) and I get

[Image: oqdZ1Sy.png]

How come an error still pulls up?

Also is there anyway to change the answer form, such that it will display a simplified answer like Wolfram?

RE: [Emulator] Laplace Transform Question - Tim Wessman - 05-30-2014 02:43 PM

factor()

Note that isn't an error, just some additional information generated during the calculation. In this case it is attempting to do some additional validation and it can't.

RE: [Emulator] Laplace Transform Question - Maro - 05-30-2014 03:05 PM

Hi Tim,

even if this isn't an error but an additional information, it is rather meaningless to always show this message. It makes working with Laplace Transformation quite inconvenient, since it shows up for each transformation and even for the most simple ones like laplace(1) = 1/s where definitely no further validation is needed. Thus it is in no way helpful for the user and makes no sense for the user to get such a message in each case. And since the validation algorithm ALWAYS reports "Unable to check …." the whole algorithm makes no sense ...

There was no need for this before the update, why now?? Look at the HP50g, everything works fine. At least the user should be able to switch off such meaningless messaging.

RE: [Emulator] Laplace Transform Question - Helge Gabert - 05-30-2014 05:09 PM

I agree, +1.

RE: [Emulator] Laplace Transform Question - parisse - 05-30-2014 05:55 PM

I'll disable the integration warning when called from laplace. It's always difficult to make meaningfull warnings that do not have side-effects:-)

RE: [Emulator] Laplace Transform Question - Maro - 05-30-2014 08:32 PM

Great! Thanks for this.

RE: [Emulator] Laplace Transform Question - Steve Keeley - 05-31-2014 12:14 AM

Also is there anyway to change the answer form, such that it will display a simplified answer like Wolfram?

Apply the algebra "Factor" function to the answer.

RE: [Emulator] Laplace Transform Question - Brad Barton - 05-31-2014 12:40 AM

Quote:Also is there anyway to change the answer form, such that it will display a simplified answer like Wolfram?

collect(ans) does the trick as well.