simpy Definition and 2 Threads

I have an expression of a vector field ##\vec J = J_r \hat r + J_\theta \hat \theta## in polar coordinates, in a region that's a quarter of an annulus, where theta ranges between 0 and pi/2 and r goes from ri to ro. I need to compute ##-\int _\Omega T(S_{xx}-S_{yy}) \frac{\partial J_x}{\partial...

I would like to evaluate expressions with Simpy, but unfortunately I am unable to get a simple answer, the one I would get by hand if I had the time to perform all the computations. As far as I understand, Mathematica does it and yields 4 times the Simpy result, which is a big worry since I wish...