2016-09-08 01:59:52 +0100 received badge ● Famous Question (source) 2015-10-21 20:10:33 +0100 received badge ● Notable Question (source) 2013-06-13 18:39:17 +0100 received badge ● Popular Question (source) 2012-05-02 16:30:09 +0100 received badge ● Editor (source) 2012-05-02 16:29:53 +0100 answered a question Integrate() does not integrate I have the Solution (partly) The function was wrong, it came up because i wrecked it with a faulty transformation. However I was able to do the first Step of integration with the "faulty" function. IN: var('a b') ftrick = -sqrt(r^2*a + b) BItrick = integral(ftrick, (r,r1,r2))  OUT: Is a positive or negative?  IN: view('AHA!') assume(a<0) assume(b>0) BItrick = integral(ftrick, (r,r1,r2)) view(BItrick) forget() BItrick2 = BItrick.substitute(a == -2*cos(phi)^2) BItrick2 = BItrick2.substitute(b == 25 ) view(BItrick2)  BItrick2 = 1/4*(6*sqrt(-18*cos(phi)^2 + 25)*cos(phi)^2 + 25*sqrt(2)*sqrt(cos(phi)^2)*arcsin(3/5*sqrt(2)*sqrt(cos(phi)^2)))/cos(ph\ i)^2 - 5/4*(2*sqrt(-50*cos(phi)^2 + 25)*cos(phi)^2 + 5*sqrt(2)*sqrt(cos(phi)^2)*arcsin(sqrt(2)*sqrt(cos(phi)^2)))/cos(phi)^2  When I try to go on sage says it doent know wheather cos(phi) ist positive or negative. So i divided the integral. forget() assume(cos(phi) >0) erg1 = integral(BItrick2, (phi,phi1,0.5*pi)) forget() assume(cos(phi) <0) erg2 = integral(BItrick2, (phi,0.5*pi,1.5*pi)) forget() assume(cos(phi) >0) erg3 = integral(BItrick2, (phi,1.5*pi,2*pi)) erg = erg1+erg2+erg3  Sage does calculate for 2 minutes and then it gives me the input. The system is unable to integrate. If you have problems with Integrations try using assume() and forget() Thank you for your Help. 2012-05-02 05:04:56 +0100 commented answer Integrate() does not integrate numerical calculation over simsons rule may be usefull in some cases, thanks. If you want to do this in SAGE you jus need to (i think) taylor-approximate the function and have an easy life with Integration. I will remeber that when i dont need symbolics. 2012-05-02 04:00:00 +0100 commented question Integrate() does not integrate I want to do things symbolic. When i did it in maple yesterday, it gave me nonsense. If even \$ got Problems with such an equation, maybe it should be an feature request. Unfortuantly iam just a student of mechanical engineering, so i cant jugdge this situation. (Is it my fault or the CAS's, i suspect mine) I,however, can do it with my own sweat and tears. Thank you so far. UPDATE: Wolfram Mathematica semms to be unable to do it (at least when you go the simple way and just tell it to Integrate) 2012-05-01 17:32:15 +0100 received badge ● Student (source) 2012-05-01 15:42:17 +0100 asked a question Integrate() does not integrate Good Evening When I ask sage: var('phi r') phi1 = 0 phi2 = 2*pi r1 = 3 r2 = 5 fpolar = - sqrt(-2*r^2*cos(phi)^2+25) BI = fpolar BI= integral(BI, (phi,phi1,phi2)) BI= integral(BI, (r,r1,r2)) BI  the result is: -integrate(integrate(sqrt(-2*r^2*cos(phi)^2 + 25), phi, 0, 2*pi), r, 3, 5)  I've found no way to make sage integrate the expresion. It repeats my input and iam not given any new information. When i try BI.n()  i get ValueError: Integrand has wrong number of parameters  Same Problem with indefinite Integrals in: BI = fpolar BI= integral(BI, phi) BI  out: -integrate(sqrt(-2*r^2*cos(phi)^2 + 25), phi)  Why? what do I need to do to get the desired output?