- #1
jameson2
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Homework Statement
Compute the area element for elliptic cylinder coordinates
Homework Equations
The coordinates are defined as follows:
x=a*cosh(u)*cos(v)
y=a*sinh(u)*sin(v)
The Attempt at a Solution
Starting from the assumption that the area element dA=dx*dy, I found dx and dy:
dx=a*du*sinh(u)*cos(v) - a*cosh(u)*dv*sin(v)
dy=a*du*cosh(u)*sin(v) - a*sinh(u)*dv*cos(v)
Then multiplying these together, to get dA:
dA=[(a^2)*sinh(u)*cosh(u)*sin(v)*cos(v)*(du^2 - dv^2)] +
[(a^2)*du*dv*((sinh(u))^2)*((cos(v))^2) - (cosh(u))^2)*((sin(v))^2)]
I don't like this answer for a couple of reasons. It seems like there should be a tidier, more compact expression than what I have. Compared to surface elements in other coordinate systems, this is frankly a mess. Also, I don't think I've seen a "du^2" in any area element formulae either, which I'm not sure makes it wrong, but I feel a little uneasy about it anyway.