- #1
randomcat
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Homework Statement
Suppose that F = ∇f for some scalar potential function f(x, y) = 1/2(x2 + y2)
Let C denote the positively oriented unit circle, parametrized by r(t) = (cos t, sin t), 0 ≤ t ≤ 2∏. Compute the flux integral of [itex]\oint[/itex]F[itex]\bullet[/itex]N ds, where N is the outward unit normal to C.
Homework Equations
I know that the theorem is basically [itex]\oint[/itex]F[itex]\bullet[/itex]N ds = double integral of ([itex]\frac{\partial M}{\partial x}[/itex] + [itex]\frac{\partial N}{\partial y}[/itex]) dx dy
My question is, how do you find F(x, y)? I'm given f(x, y) in the problem, but do I need to use it to solve for the answer?
The Attempt at a Solution
What I did (which was wrong) was that I set M = 1/2x2 and N = 1/2y2 and took the partial derivatives of those. That gives me (x, y). With the parametrization, I get (cos t, sin t). Then I integrate them over the unit circle and got 0, which was wrong. The correct answer is 2pi.
My professor wrote that F = ∇f = F(x, y) in the solutions, but where did F(x, y) come from?