Laplace function a bit limited
11-05-2016, 11:42 PM
Post: #1
 hsauro Junior Member Posts: 4 Joined: Nov 2016
Laplace function a bit limited
Just got a new HP prime C series. I tried some Laplace transform derivations and the first two I picked failed, these were:

1/t

which I entered as laplace (1/t, t, s)

it returned undef

and

(1-e^{-t})/t

entered as laplace ((1-e^(-t))/t, t, s)

returned undef.

Question is have I entered the equations incorrectly or is the CAS just limited? The 1/t in particular is a standard function to get the laplace transform of, its just 1/s^2.
11-06-2016, 12:40 AM (This post was last modified: 11-06-2016 12:44 AM by Mark Hardman.)
Post: #2
 Mark Hardman Senior Member Posts: 525 Joined: Dec 2013
RE: Laplace function a bit limited
On my first day of Filter Design 214 I learned:

ℒ[t] = 1/s^2

https://www.wolframalpha.com/input/?i=laplace(t,t,s)

Just saying...

Mark Hardman

Ceci n'est pas une signature.
11-06-2016, 01:37 AM
Post: #3
 hsauro Junior Member Posts: 4 Joined: Nov 2016
RE: Laplace function a bit limited
(11-06-2016 12:40 AM)Mark Hardman Wrote:  On my first day of Filter Design 214 I learned:

ℒ[t] = 1/s^2

https://www.wolframalpha.com/input/?i=laplace(t,t,s)

Just saying...

Mark Hardman

Of course I know what the Laplace transform of t is. What I wanted to know was whether the calculator knew, obviously it didn't. As I said, this was surpring for such a basic transform. It suggests to me that the Cas capability at least for Laplace transforms might be limited. I shall need to try some more.
11-06-2016, 01:47 AM (This post was last modified: 11-06-2016 01:51 AM by Mark Hardman.)
Post: #4
 Mark Hardman Senior Member Posts: 525 Joined: Dec 2013
RE: Laplace function a bit limited
(11-06-2016 01:37 AM)hsauro Wrote:  Of course I know what the Laplace transform of t is. What I wanted to know was whether the calculator knew, obviously it didn't. As I said, this was surpring for such a basic transform. It suggests to me that the Cas capability at least for Laplace transforms might be limited. I shall need to try some more.

No, you said the following:

(11-06-2016 01:37 AM)hsauro Wrote:  The 1/t in particular is a standard function to get the laplace transform of, its just 1/s^2.

Which is demonstratively false.

The CAS is telling you that there is no standard form for:

ℒ[1/t]

WolframAlpha agrees.

https://www.wolframalpha.com/input/?i=la...1%2Ft,t,s)

"(no result found in terms of standard mathematical functions)"

Mark Hardman

Ceci n'est pas une signature.
11-06-2016, 01:58 AM (This post was last modified: 11-06-2016 02:03 AM by hsauro.)
Post: #5
 hsauro Junior Member Posts: 4 Joined: Nov 2016
RE: Laplace function a bit limited
(11-06-2016 01:47 AM)Mark Hardman Wrote:
(11-06-2016 01:37 AM)hsauro Wrote:  Of course I know what the Laplace transform of t is. What I wanted to know was whether the calculator knew, obviously it didn't. As I said, this was surpring for such a basic transform. It suggests to me that the Cas capability at least for Laplace transforms might be limited. I shall need to try some more.

No, you said the following:

(11-06-2016 01:37 AM)hsauro Wrote:  The 1/t in particular is a standard function to get the laplace transform of, its just 1/s^2.

Which is demonstratively false.

The CAS is telling you that there is no standard form for:

ℒ[1/t]

WolframAlpha agrees.

https://www.wolframalpha.com/input/?i=la...1%2Ft,t,s)

"(no result found in terms of standard mathematical functions)"

Mark Hardman

My bad I apologize, don't know why I typed in 1/t ! Prime certainly can do t.

Anyone one reading this thread, it's a false alarm, sorry for the confusion.
11-06-2016, 02:06 AM
Post: #6
 hsauro Junior Member Posts: 4 Joined: Nov 2016
RE: Laplace function a bit limited
(11-06-2016 01:58 AM)hsauro Wrote:  [quote='Mark Hardman' pid='63693' dateline='1478396852']

No, you said the following:

Which is demonstratively false.

The CAS is telling you that there is no standard form for:

ℒ[1/t]

WolframAlpha agrees.

https://www.wolframalpha.com/input/?i=la...1%2Ft,t,s)

"(no result found in terms of standard mathematical functions)"

Mark Hardman

If any one has the power to delete threads this is one that should probably be deleted in case it inadvertently mismlead ssomeone, since the original premise is incorrect.
11-06-2016, 02:27 AM
Post: #7
 CH3791 Junior Member Posts: 40 Joined: May 2016
RE: Laplace function a bit limited
You can delete threads yourself. Just click edit>full edit and on the top there is an option to delete.
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