I have constructed a formula to represent the neutron flux from a disc emitter through an aperture. I have got it down to a double integral of a form that I can't see how to evaluate. Mathematica crashes on this and I am not ready yet to give up and go to numerical solution. Does anyone know a good technique for evaluating integrals of this type? Int dTheta*Sin(2*Theta)*Sqrt[A^2-(r-D*Tan(Theta))^2] It is a product of a trig function and then a sqrt with a trig function inside. Integration by parts doesn't improve the radical and I'm looking for analytic solution if possible...any ideas?