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Green's Theorem




The theorem statement is the following. Let ''C'' be a positively oriented, Piecewise Smooth , Simple Closed Curve in the plane and let ''D'' be the region bounded by ''C''. If ''L'' and ''M'' have continuous Partial Derivatives on an open region containing ''D'', then

:\int_{C} L\, dx + M\, dy = \iint_{D} \left( rac{\partial M}{\partial x} - rac{\partial L}{\partial y} ight)\, dA.

Sometimes a small circle is placed on top of the integral symbol:

:\oint_{C}

This indicates that the curve ''C'' is closed. To indicate positive orientation, an arrow pointing in the counter-clockwise direction is sometimes drawn in the circle over the integral symbol.


PROOF OF GREEN'S THEOREM WHEN ''D'' IS A SIMPLE REGION


If it can be shown that

:\int_{C} L\, dx = \iint_{D} \left(- rac{\partial L}{\partial y} ight) dA\qquad\mathrm{(1)}

and

:\int_{C} M\, dy = \iint_{D} \left( rac{\partial M}{\partial x} ight)\, dA\qquad\mathrm{(2)}

are true, then Green's theorem is proven.

We define a region ''D'' that is simple enough for our purposes. If region ''D'' is expressed such that: