Path: news.mathworks.com!not-for-mail From: <HIDDEN> Newsgroups: comp.soft-sys.matlab Subject: Re: Warning: Explicit integral could not be found. Date: Sun, 3 Jul 2011 01:24:09 +0000 (UTC) Organization: The MathWorks, Inc. Lines: 14 Message-ID: <iuogbp$fih$1@newscl01ah.mathworks.com> References: <iuo7gj$oi7$1@newscl01ah.mathworks.com> Reply-To: <HIDDEN> NNTP-Posting-Host: www-05-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: newscl01ah.mathworks.com 1309656249 15953 172.30.248.37 (3 Jul 2011 01:24:09 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Sun, 3 Jul 2011 01:24:09 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 1187260 Xref: news.mathworks.com comp.soft-sys.matlab:734679 "Ashwin Balaji" <ashwinb1@umbc.edu> wrote in message <iuo7gj$oi7$1@newscl01ah.mathworks.com>... > I need to Integrate the below function, but when I use the int(fun,R,1,2) command in Matlab it returns to me with an error saying "Explicit integral could not be found". > > (2*R^-9) + (A*R^-11) / ((A+R^2)^2) > > I am integrating over the limits [1,2] with respect to R and A is a constant. Could you please help and guide me through this problem. How do we obtain solutions to such Integrals using Matlab. I would come across many more similar integrals in my work which I would need to solve, so please guide me through the solution for these kind of problems. > I need the answer for this integral to be in terms of constant A. So that further apply my conditions I could solve for A > > Thanks, > Ashwin - - - - - - - - - - My own ancient version of 'solve' managed to handle that (with a rather messy solution.) I don't see why later versions should be less skillful than mine. Mine did make the rather unwarranted assumption that the quantity A+R^2 was always positive throughout the R range from 1 to 2 when it used log(A+R^2) in the indefinite integral at one point. Perhaps your version is more careful about that and wants more information about A before committing itself. If A is actually supposed to be positive, you might try using B^2 in place of A to see if that would remove its doubts since there is no chance that B^2+R^2 could be negative. Roger Stafford