Recognition of Solids
69. Meet the Cone · Tapering from a circle to a point
The shape always tapers from a circular base to a single vertex.
A cone is a 3D solid with a circular base that tapers smoothly to a single point called the apex (or vertex). Examples: ice-cream cone, party hat, pencil tip.
What this lesson covers
Try to break it
Drag the height handle H up and down. Notice how the cone gets taller or shorter, but it always stays a cone!
How you build it
Construct a cone.
- Mark the centre point O of the base.
- With centre O, draw the circle that forms the base.
- Mark point V — the vertex — straight above the centre O.
- Draw the segment from O up to V — this is the height of the cone.
- Draw a segment from V to the left edge of the base circle — a slant side.
- Draw a segment from V to the right edge of the base circle — the other slant side.
The proof, step by step
Prove that the solid is a cone — a circular base tapering to a single vertex.
- A cone has a circular base.
- A cone has exactly one vertex.
- The curved surface connects the base to the vertex.
Worked example
A solid object has one circular base, one vertex, and one curved surface. What is it called?
A cone is defined by having a circular base, a single vertex, and a curved surface connecting them.
- Cylinder
- Cone — correct
- Sphere
- Pyramid