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+--- Thread: integrating with the HP Prime (/thread-7222.html)
integrating with the HP Prime - Fanboy - 11-12-2016 08:35 AM
I'm trying to integrate 'e^(-B*x^2) from -inf to +inf' with the hp prime emulator. The calculator is not spitting out what I'm looking for which is sqrt(pi/B) and incorrectly gives infinity as the answer.
However, it gives the correct answer (sqrt(pi)) when I just integrate 'e^(-x^2) from -inf to +inf' (without any letters). If I use a number instead of a letter, then it starts giving out the correct answer again. I'm completely new to the prime (currently have a 50G) so can anyone tell me how to get my answer in terms of the letter?
I've posted a pic of the problem here:
http://i1226.photobucket.com/albums/ee408/ForsakenSteel/HP%20Prime%20INT_zps09rhavgy.png
RE: integrating with the HP Prime - parisse - 11-12-2016 10:28 AM
You should not use B as parameter, because B is always assigned on the Prime, by default to 0.0, and since exp(-B*x^2)=1 if B=0 this explains why the integral is infinity. Try with b instead.
RE: integrating with the HP Prime - Fanboy - 11-12-2016 11:15 PM
How do we know which letters have a value attached to them like B? I noticed that the letters 'K' and 'A' also gave infinity as the answer.
Also, if I use another letter like b or a, I get the answer as "undef". Its still not working.
RE: integrating with the HP Prime - roadrunner - 11-13-2016 12:01 AM
You have to tell it that b isn't negative.
Try typing: assume(b≥0)
Then type: ∫(e^((-b)*x^2),x,-(∞),∞)
You should get: √(π)/√(b)
[attachment=4142]
-road
RE: integrating with the HP Prime - Fanboy - 11-13-2016 12:21 AM
Ok, that works. How do I remove that assumption?
RE: integrating with the HP Prime - roadrunner - 11-13-2016 12:44 AM
(11-13-2016 12:21 AM)Fanboy Wrote: How do I remove that assumption?
purge(b)