Answer:
hyperbola
Step-by-step explanation:
That conic section is a hyperbola.
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parallel to the base: circle
oblique to the base, but at an angle less than the side angle: ellipse
parallel to the side: parabola
oblique to the base at an angle greater than the side angle: hyperbola. This plane of intersection crosses both naps of the cone, so results in two disjoint curves.