Slice a 3D solid and look at the flat shape you reveal — that is the cross section!
A CROSS SECTION is the 2D shape you see when you make a flat cut through a 3D solid. Different cuts of the same solid can reveal different shapes. Visualizing cross sections builds powerful spatial reasoning.
Slice a cube: • Horizontally (parallel to base) → square • Diagonally (edge to edge) → rectangle • Cutting through 6 faces diagonally → hexagon! The same solid yields many different cross sections depending on angle.
Cross sections of a cone
Cross sections of a cylinder
The angle and direction of the cut determines which 2D shape appears!
How to determine a cross section:
Cross sections of a rectangular pyramid:
Higher horizontal cuts give smaller rectangles because the pyramid narrows toward its apex.
If you slice a sphere with a flat cut through its center, what shape is the cross section?
Remember This!
Try it at home! Slice an orange or a bell pepper in different directions. The cross-sectional shapes change depending on whether you cut horizontally, vertically, or at an angle.