A plane intersects a double-napped cone so that it makes an angle of 41o with the central axis. The conic form is an ellipse. The vertex angle of the cone must be less than . . .

2. Hello, alexanderl33!;198760]

A plane intersects a double-napped cone and makes a 41° angle with the central axis.
The conic formed is an ellipse. The vertex angle of the cone must be less than . . .

Consider a cone with an 82° vertex angle.
The configuration looks like this.
Code:
              *
/|\
/ | \
/  |  \
/41°|41°\   /
/    |    \ /
/     |     *
/      |    / \
/       |41°/   \
/        |  /     \
/         | /       \
/          |/         \
/           *           \
/           /             \

The intersecting plane is parallel to the slant of the cone.
The resulting conic curve would be a parabola.

For the plane to pass through the cone,
. . the vertex angle must be less than 82°.