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Figures 3.3.9(a, b) each contains a graph of the surface defined by the given equation,
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whose standard form is
obtained by completing the square in and . The standard form is the equation of an elliptic paraboloid with center .
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The level curves, drawn on the surface of the quadric, are the ellipses
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The cross sections and are parabolas, shown in Figures 3.3.9(a, b) where the sliders control the values of . Indeed, if , then the equation
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defines parabolas in the -plane, seen in Figure 3.3.9(a). Likewise, the cross sections are the parabolas
defined in the -plane, and shown in Figure 3.3.9(b).
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Figure 3.3.9(a) Elliptic paraboloid with cross sections
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Figure 3.3.9(b) Elliptic paraboloid with cross sections
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