A generalization of the helicoid to the parametric equations
(1)
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(2)
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(3)
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In this parametrization, the surface has first fundamental form coefficients
(4)
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(5)
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(6)
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and second fundamental form coefficients
(7)
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(8)
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(9)
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The Gaussian and mean curvatures are given by
(10)
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(11)
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