Path: news.mathworks.com!not-for-mail From: <HIDDEN> Newsgroups: comp.soft-sys.matlab Subject: Re: Calculating the limit of an integral Date: Fri, 30 Mar 2012 13:52:12 +0000 (UTC) Organization: The MathWorks, Inc. Lines: 23 Message-ID: <jl4dqc$f8c$1@newscl01ah.mathworks.com> References: <jl2mtk$a37$1@newscl01ah.mathworks.com> <jl3017$adm$1@newscl01ah.mathworks.com> Reply-To: <HIDDEN> NNTP-Posting-Host: www-04-blr.mathworks.com Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Trace: newscl01ah.mathworks.com 1333115532 15628 172.30.248.35 (30 Mar 2012 13:52:12 GMT) X-Complaints-To: news@mathworks.com NNTP-Posting-Date: Fri, 30 Mar 2012 13:52:12 +0000 (UTC) X-Newsreader: MATLAB Central Newsreader 3403027 Xref: news.mathworks.com comp.soft-sys.matlab:762683 "Roger Stafford" wrote in message <jl3017$adm$1@newscl01ah.mathworks.com>... > "Haojie" wrote in message <jl2mtk$a37$1@newscl01ah.mathworks.com>... > > ..... I have a implicit equation that the limit (t) is unknow. And t is also in the integrand. x is the variable > > The equation is like > > int(sqrt(A*x^(2/7)-A*t^(2/7)),0,t)-int(sqrt(A*t^(2/7)-A*x^(2/7),t,1)=0 > > I want to solve for t numerically ....... > - - - - - - - - - > I assume A is a negative scalar. Otherwise you would be taking the square roots of negative quantities. Other than that I don't see the purpose in including A here. The square root of -A can be factored out. > > Also you are missing a right parenthesis on the second square root. > > You can probably solve this using matlab's 'fzero' routine. However, its function handle will have to be written so as to perform numerical quadrature on a vector of different t values passed to it, two integrations for each t element. > > Roger Stafford Thanks for your reply. Do you mean I should write like this? function y1 = f1(x); function y2 = f2(x); y1 = sqrt(t^(2/7)-x^(2/7)); y2 = sqrt(x^(2/7)-t^(2/7)); Q1 = quad(@f1,0,t); Q2 = quad(@f2,t,1); But then I dont know how to use fzero to calculate t, because Q1 - Q2=0 is not a function so cannot be used in fzero. I dont know if you mean this or please correct me if I understand wrong