- #1
gtfitzpatrick
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Homework Statement
find a simple closed curve with counter-clockwise orientation that maximises the value of [itex]\oint (cos x^2 + 4yx^2) dx + (4x-xy^2)dy[/itex]
Homework Equations
The Attempt at a Solution
from greens theorem [itex]\oint Pdx+qdy = \int\int \frac{\partial q}{\partial x} - \frac{\partial p}{\partial y} dA[/itex]
so[itex]\int\int_{D} 4-y^2-4x^2 dxdy[/itex]
the integrand is positive everywher inside the elipse,zero on the ellipse and negative outside. so to maximise the integral C should be the oriented boundary of the ellipse oriented in the counter-clockwise direction.
x=2cosr y=sinr dx=rdr
sooo i think the maximum value is [itex]\int^{2\pi}_{0} \int^{2}_{0} 4 - sin^2 r - 16 cos ^2 r drd\theta[/itex]
which i the simplify.
anyone know if I'm on the right lines here...