A plane intersecting a double-napped cone makes a 55° angle with the central axis. The angle between the generator and the central axis is 35°.Which conic section is formed?

Compare the plane’s angle with the axis, 55°, to the generator’s angle with the axis, 35°. Since 55° is greater than 35°, the plane cuts only one nappe and is not parallel to a generator, so the cross-section is an ellipse. The correct choice is ellipse.

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