A surface generated by the parametric equations
(1)
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(2)
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(3)
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The above image uses and .
The coefficients of the first fundamental form are
(4)
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(5)
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(6)
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the coefficients of the second fundamental form are
(7)
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(8)
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(9)
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the area element is
(10)
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and the Gaussian and mean curvatures are given by
(11)
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(12)
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