#### AwesomeTrains

Gold Member

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**1. The problem statement, all variables and given/known data**

Hello

I was given the vector field: [itex]\vec A (\vec r) =(−y(x^2+y^2),x(x^2+y^2),xyz)[/itex] and had to calculate the line integral [itex] \oint \vec A \cdot d \vec r [/itex] over a circle centered at the origin in the [itex]xy[/itex]-plane, with radius [itex] R [/itex], by using the theorem of Stokes.

Another thing, when calculating [itex]∇× \vec A [/itex] I used Cartesian coordinates but when doing the integration I changed to polar coordinates, is that okay? Or do I have to do it all in Cartesian coordinates, because I did curl in Cartesian coordinates?

**2. Relevant equations**

Stokes equation:

**3. The attempt at a solution**

My result is: [itex]2R^4π[/itex] Is that correct ? I evaluated both sides and got the same.

Kind regards Alex