Answer :
When the plane intersects the polygon at any given two adjacent sides of the base.
Answer:
when the plane makes a narrow angle with the base.
Step-by-step explanation:
Given: A prism with a Nonagon as base.
To find: When a cross section be a Decagon.
Nonagon is a polygon with 9 sides
Decagon is a polygon with 10 sides.
1). when a cross section is taken parallel to the base, the cross section will be Nonagon .i.e., it will be a 9 sided polygon.
2).when a cross section is taken perpendicular to the base, the cross section will be a rectangle.
3). when a slant cross section is taken .i.e., one with any angle other than 90° or 180° to the base. It will be a 10-sided polygon.