Showing a vector field is irrational on

tamintl
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Homework Statement


Let F = ( -y/(x2+y2) , x/(x2+y2) ) Show that this vector field is irrotational on ℝ2 - {0}, the real plane less the origin. Then calculate directly the line integral of F around a circle of radius 1.

Homework Equations


The Attempt at a Solution



To show F is irrotational we must show curl v = 0. Although I'm unsure what it means by finding it on ℝ2 - {0} ?
 
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It just means find the curl at a general point (x,y) where x and y aren't both 0. The vector field is undefined at (0,0).
 
okay thanks.. I got it
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...

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