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frequencydrive
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HP Prime Laplace Transform "undef" using CAS mode

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I am taking a Control Systems class as part of my electrical engineering degree.  I have to do some Laplace Transforms regularly so I would like to be able to take the Laplace Transform of a time domain function.

 

I am trying to do this in CAS mode (by pusing CAS button).   I normally use RPN mode in HOME.  But some things seems to be less troublesome if I use CAS mode so that is the mode I am in when trying this stuff.  If I type this:

 

laplace(exp(t)*Sin(t),t,s)       the calculator says "undef". 

 

I am not typing in "laplace" I am using the toolbox -> Calculus-> Transform->Laplace.  I do not have any user variables defined as 's' or 't'.  If I type   purge(s,t)   the calculator returns  ["no such variable s"  "no such variable t"].

 

I have read the manual.  On page 370 it shows the following for Laplace Transform:

 

laplace(exp(x)*sin(x)) gives 1/(x^2-2*x+2) 

 

If I type that the calculator gives me an error stating "undef"

 

Can someone please help me figure this out?  This should be pretty straightforward but it's not going well for me.  I am thinking it has something to do with the variables chosen or even capitalization or maybe my CAS settings.  

 

Please help me.  I'm dying here.

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frequencydrive
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I am the OP.   I found the solution.  When you are doing Laplace Transforms you need to have your angle mode set to RADIANS.  I can't believe the calculator doesn't pop up a box telling you that is why it can't do the Laplace transform.  Just stating "undef" does not indicate what exactly the problem is. 

 

You know I found out what it was by trying the same thing in the emulator on my laptop.  I started the emulator and then I tried to take the laplace transform of this function:

 

laplace(3*e^t,t,s) and the emulator said "This function works only in radian mode Error: Bad argument value"  

 

That is **bleep**ed up.  The HP50g tells you when you need to be in radian mode and even offers to automatically switch to that mode before continuing.  Those guys at HP need to  look at stuff like this.  I have spend about 2 hours trying to figure this out and if it wasn't for the emulator I wouldn't have a clue how to use the Laplace Transform function.

 

I hope I helped someone.

Tim_Wessman
Level 8
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You should update your calculator I think. I just did this on mine here with the latest and get "This function only works in radians mode" returned... 🙂

TW

Although I work for the HP calculator group as a head developer of the HP Prime, the views and opinions I post here are my own.
frequencydrive
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I was unaware of any updates. I have updated my calculator I think there was an update on 1-24-2018.
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Maké
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Hi!, @frequencydrive:

 

No needed actualize, the firmware. Only needed put CAS MODE and ...

Laplace.PNG 

 

And with, Wolfram Alpha ... https://www.wolframalpha.com/input/?i=laplace(exp(x)*sin(x))&rawformassumption=%7B%22FunClash%22,+%2...

Kind Regards !.
Have a nice day !.
@Maké (Technical Advisor Premium - HP Program Top Contributor).
Provost in HP Spanish Public Forum ... https://h30467.www3.hp.com/
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Felipe-Zucchi
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Ola estou tendo dificuldades em fazer algumas transformadas de laplace

por exemplo a sen(5t)*cis(2t) na minha da um resultado nada haver ( cos(2t)*sin(2t))/x sendo que o resultado correto seria (1/2)*((7/s+49)+(3/(s

^2+9))

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Maké
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Hi!, @Felipe-Zucchi :

Este é um Fórum de Ajuda em Idioma Inglês, portanto, você deve escrever nesse idioma from https://h30487.www3.hp.com/

O resultado que está dando para você, está em coordenadas polares, que de acordo com o Wolfram Alpha, é ...

Polar.PNG

 

 

 

Kind Regards !.
Have a nice day !.
@Maké (Technical Advisor Premium - HP Program Top Contributor).
Provost in HP Spanish Public Forum ... https://h30467.www3.hp.com/
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