
Re: Warning: Explicit integral could not be found.
Posted:
Jul 22, 2013 5:21 AM


On 26.06.13 03:26, Ferra wrote:
> I'm trying to solve this integration but it gives me this error: > Warning: Explicit integral could not be found. > > syms a b > Q = (1/(2*pi*lams)) * exp(  (a^2 + b^2)/(2*lams)); > q = int(int(Q,b,0,sqrt((lams^2)  (a^2))),a,0,lams);
I'm not sure what lams is, but even assuming it is an unspecified symbolic variable, changing the order of integration yields a closedform integral:
>> syms lams >> q = int(int(Q,a,0,lams),b,0,sqrt((lams^2)  (a^2)))
q =
(5734161139222659*pi*erf((2^(1/2)*lams)/2)*erf((2^(1/2)*(lams^2  a^2)^(1/2))/2))/72057594037927936
SMT neither has some explicit notion of ?double integral,? nor does it check whether your integrand fulfills the conditions of Fubini's theorem to allow exchanging the order of integration (which happens to be the case here, at least if a, b, and lams are finite and real, and lams is positive). That is something you need to do yourself.
HTH,
Christopher

