youcubed: Reduce, Reuse, Geometry (3-12)
youcubed (Stanford University)

Intersecting a 3D shape and a plane might seem intimidating, but a few bottles, a box cutter, and some creativity can give us some insight into what it can look like.

GeoGebra: Exploring Intersections of Planes
GeoGebra

Suppose 2 planes intersect. How would you describe their intersection?