They built the foundation up making it smaller every time because of the square base.
triangle... because pyramids are triangular therefore triangular pyramids have triangle faces
They both have a triangular shape
The pyramids of Egypt were built in a triangular shape to represent a mound. The shape was a representation of the Egyptian belief that the Earth came from a mound. Note that while the pyramids are triangular from the side, they actually occupy a square footprint (i.e. square pyramids). This was in order to align the pyramids with the cardinal directions.
Pyramids.
Pyramids have some triangular faces.
A hexahedron or a triangular dipyramid. This is the shape formed by two triangular pyramids (tetrahedrons) stuck together along one triangular face.
The shape of its base. So you can get triangular pyramids, square pyramids and so on.
Pyramids are constructed from triangular shapes and can have square or triangle bases
A triangular dipyramid - two triangular pyramids stuck together.
Triangles, pyramids, and prisms can all have triangular shapes.
A hexahedron in the form of a triangular bipyramid: two triangular pyramids stuck together.
Triangular prisms and Rectangular pyramids