Integration Question HP50g
10-16-2016, 10:15 AM
Post: #1
 Fanboy Junior Member Posts: 13 Joined: Mar 2014
Integration Question HP50g
I'm trying to integrate e^-(ax^2) dx from -inf to +inf. When I use PREVAL, it says unsigned inf error. When I use use equation editor to find the answer, it just keeps adding t in the expression. Wolfram alpha does it correctly:
https://www.wolframalpha.com/input/?i=%E...+to+%2Binf

I know I might have to make an assumption that the 'a' in my expression is greater than 0 but I don't know how to do so. So any suggestions?

Also, are all the integration functions equal or are some better than the other. For eg, for definite integrals, are PREVAL, INT, and using the equation editor methods all equal? or is one inherently better than the other?
10-16-2016, 02:33 PM
Post: #2
 rprosperi Senior Member Posts: 3,308 Joined: Dec 2013
RE: Integration Question HP50g
(10-16-2016 10:15 AM)Fanboy Wrote:  I'm trying to integrate e^-(ax^2) dx from -inf to +inf. When I use PREVAL, it says unsigned inf error. When I use use equation editor to find the answer, it just keeps adding t in the expression. Wolfram alpha does it correctly:
https://www.wolframalpha.com/input/?i=%E...+to+%2Binf

I know I might have to make an assumption that the 'a' in my expression is greater than 0 but I don't know how to do so. So any suggestions?

Also, are all the integration functions equal or are some better than the other. For eg, for definite integrals, are PREVAL, INT, and using the equation editor methods all equal? or is one inherently better than the other?

Not sure if this is the only issue, but you must have a "*" between 'a' and 'x', implicit multiplication isn't allowed.

Must be a homework assignment somewhere, 2nd time in a week....

--Bob Prosperi
10-16-2016, 06:14 PM
Post: #3
 peacecalc Member Posts: 138 Joined: Dec 2013
RE: Integration Question HP50g
Hello fanboy,

you can use the hp 50g CAS for integrating this, but there are manually several steps necessary. Of course with the input correction rprosperi mentioned.

The integral is not a simple one. The CAS of wolfram alpha is much mighter than that one in hp 50g.
10-17-2016, 02:51 AM
Post: #4
 Fanboy Junior Member Posts: 13 Joined: Mar 2014
RE: Integration Question HP50g
(10-16-2016 02:33 PM)rprosperi Wrote:
(10-16-2016 10:15 AM)Fanboy Wrote:  I'm trying to integrate e^-(ax^2) dx from -inf to +inf. When I use PREVAL, it says unsigned inf error. When I use use equation editor to find the answer, it just keeps adding t in the expression. Wolfram alpha does it correctly:
https://www.wolframalpha.com/input/?i=%E...+to+%2Binf

I know I might have to make an assumption that the 'a' in my expression is greater than 0 but I don't know how to do so. So any suggestions?

Also, are all the integration functions equal or are some better than the other. For eg, for definite integrals, are PREVAL, INT, and using the equation editor methods all equal? or is one inherently better than the other?

Not sure if this is the only issue, but you must have a "*" between 'a' and 'x', implicit multiplication isn't allowed.

Must be a homework assignment somewhere, 2nd time in a week....

That '*' is not the problem. I have that when I enter it in the 50g. I just typed it here that way.
10-17-2016, 07:54 AM
Post: #5
 Vtile Senior Member Posts: 384 Joined: Oct 2015
RE: Integration Question HP50g
10-17-2016, 05:20 PM
Post: #6
 peacecalc Member Posts: 138 Joined: Dec 2013
RE: Integration Question HP50g
Hello Fanboy,

have a look HERE for the integration of your integral (it is only possible for infinte limits, but there exists no antiderivate). That means the '*' doesn't do the job alone.

@Vtile, that is not the same problem.
10-17-2016, 06:12 PM (This post was last modified: 10-17-2016 06:12 PM by Vtile.)
Post: #7
 Vtile Senior Member Posts: 384 Joined: Oct 2015
RE: Integration Question HP50g
@peacecalc, My bad. I didn't read it properly, I just noticed the note that there were "the same question asked a few days ago".
10-18-2016, 06:00 AM
Post: #8
 Fanboy Junior Member Posts: 13 Joined: Mar 2014
RE: Integration Question HP50g
(10-17-2016 05:20 PM)peacecalc Wrote:  Hello Fanboy,

have a look HERE for the integration of your integral (it is only possible for infinte limits, but there exists no antiderivate). That means the '*' doesn't do the job alone.

@Vtile, that is not the same problem.

I was hoping I could somehow coax the 50g into spitting out the answer [sqrt(pi)] for that definite integral but I guess that's not possible. I was interested in that integral because that integral and its variations pop up a lot in quantum mechanics. I don't always feel like taking out my phone to use Wolfram Alpha lol.
10-18-2016, 06:17 PM
Post: #9
 peacecalc Member Posts: 138 Joined: Dec 2013
RE: Integration Question HP50g
Hello fanboy,

maybe there is a way, have a look to the commands MATCH (down arrow as a sign) or
MATCH (up arrow as a sign) in AUR (Advanced User Reference manual).
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