A cross section is the face you get when you make one slice through an object. Below is a sample slice through a cube, showing one of the cross sections you can get.
The polygon formed by the slice is the cross section. The cross section cannot contain any piece of the original face; it all comes from "inside" the solid. In this picture, only the gray piece is a cross section.
Use the Interactive Activity below to work on Problems C1 and C2. For a non-interactive version of the activity, and to work on Problems C3 and C4, you may want to use clay solids and dental floss to derive your answers. Alternatively, you may want to use colored water in plastic solids. Note 3