# The envelope of a triangular pyramid

**Lesson Aims**Investigate pyramids

- Description of a pyramid, number of faces,edges and vertices.
- Recognition of a triangular pyramid and envelope of a pyramid.
- Pyramids with different bases.

**Model Name**Envelope of a triangular pyramid.

**Lesson structure**First lesson on the topic of 3-D solids.

**Lesson content**Pupils will construct a triangular pyramid, investigate the properties of this pyramid, the envelope of this pyramid constructed from triangles and comparison of the envelope and the solid.

**Prior knowledge**Polygons and triangles.

**The envelope of a triangular pyramid**