# Chapter 13 - Vector Geometry - 13.6 A Survey of Quadratic Surfaces - Exercises - Page 692: 13

Eellipsoid; the trace is a circle in the $xz$-plane.

#### Work Step by Step

The equation $$x^2+ \left(\frac{y}{4}\right)^{2} +z^2=1$$ is an ellipsoid. To find the trace in the $xz$-plane, we put $y=0$; hence we have $$x^2+ z^2=1$$ which is a circle in the $xz$-plane. (See equations on page 691.)

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