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CAF123
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Homework Statement
Use Stokes' Theorem to evaluate $$\int_{\gamma} y\,dx + z\,dy + x\,dz,$$ where ##\gamma## is the suitably oriented intersection of the surfaces ##x^2 + y^2 + z^2 = a^2## and ## x + y + z = 0##
The Attempt at a Solution
Stokes' says that this is equal to $$\iint_S (\underline{\nabla} \times \underline{F}) \cdot \underline{n}\,dA$$ So from the question, I can extract ##\underline{F} = \langle y,z,x \rangle## and compute ##\, \text{curl}\underline{F} ##. ##\,\,####\gamma## marks the boundary of the surface S, so in using Stokes' I can use any surface whose boundary is ##\gamma##.
Let ##z = -x -y => x^2 + y^2 + (-x-y)^2 = a^2##, which when rearranged gives ##x^2 + y^2 +xy = a^2/2##. I put this into Wolfram Alpha and it is an ellipse, however I am unsure of how to show this. I.e I want to get what I have in the form ##\frac{x^2}{A^2} + \frac{y^2}{B^2} = 1.## I would complete the square but the## xy## term is annoying. Once I have it in the form of an ellipse, I am sure I can just say ##x = A\cos t, y = B\sin t## on the boundary, find normal, dot it with the curl and set the bounds. I am also a little bit unsure of what the bounds would be. If the result of curl F dotted with n resulted in 1, then I could just simply say that the surface integral is the area of the ellipse, which would greatly simplify things.
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