integration
1 Ansicht (letzte 30 Tage)
Ältere Kommentare anzeigen
please can someone help me to solve this problem: I want to integrate this function:
exp(0.5*(1-((l-hm)/(2*H))-exp(-((l-hm)/(2*H)))))
I make this program:
hm=400;
H=50;
syms l;
H0=int(exp(0.5*(1-((l-hm)/(2*H))-exp(-((l-hm)/(2*H))))),l,hm,700)
but the answer is:
100*2^(1/2)*pi^(1/2)*exp(1)^(1/2)*(erf(2^(1/2)/2) - erf(2^(1/2)/(2*exp(3/2))))
how to get the right answer???
0 Kommentare
Antworten (3)
Alexander
am 25 Mai 2012
Why do you think that the answer is incorrect? If you just want a number, use double on the result:
>> double(H0)
ans =
209.1673
Or use INTEGRAL as Mike Hosea suggests.
2 Kommentare
Mike Hosea
am 25 Mai 2012
:lol: I didn't even bother with the symbolic attempt and completely misinterpreted the question. I'm blaming this on Walter. :)
Mike Hosea
am 25 Mai 2012
I never quite know what to say when questions like this come up. There's nothing wrong with wanting to do integrals analytically, to be sure, and some times there are legitimate reasons, I guess, but I wonder what people need the analytical answer for. This problem is really no problem for INTEGRAL (or QUADGK)
>> integral(@(l)exp(0.5*(1-((l-hm)/(2*H))-exp(-((l-hm)/(2*H))))),hm,700)
ans =
2.091673274741571e+02
>> 100*2^(1/2)*pi^(1/2)*exp(1)^(1/2)*(erf(2^(1/2)/2) - erf(2^(1/2)/(2*exp(3/2))))
ans =
2.091673274741571e+02
0 Kommentare
Walter Roberson
am 25 Mai 2012
MuPAD is not able to complete that integral. (Maple is not able to do it either.)
Perhaps there is an appropriate change of variables, but I have not been able to locate one.
7 Kommentare
Christopher Creutzig
am 25 Mai 2012
If it helps to get some confidence in the result: To get integrals.com to integrate the expression (indefinitely), substitute x=exp(-l/200). http://integrals.wolfram.com/index.jsp?expr=-200*exp%285%2F2+-+%281%2F2%29*x^2*exp%284%29%29&random=false
Siehe auch
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!