Recent content by newmathman

I was referring to d_leet's post. I mean the integrals over dx dy are correct in sense that I can evalute them and then substitude the values a<x<b, c<y<d for some region. But for integrals over dr d\theta I can not first evalute them and then substitude the values r1<r<r2...

Ahaa! So my integrals over dx dy are correct by the ones over dr d\theta are not?

Why should I choose a region? When I have to evaluate a indefinite double integral, I can't apply change of variables?

Hi, everyone! I have a problem in understading the change of variables in double integrals. Here is an example \int\int x^2+y^2dx dy=\int \frac{x^3}{3}+y^2x dy=\frac{x^3y}{3}+\frac{y^3x}{3}+C_1 but if I first do a change in poral coordinates I get \int\int r^2 r...