The regular convex polyhedra are the five Platonic solids ... there are only five Platonic solids – the regular tetrahedron (four sides that are equilateral triangles), the cube (six sides that are ...

A 3D shape with all straight edges and flat faces is a polyhedron ... a triangular base is a triangle-based pyramid. A tetrahedron is a triangular pyramid with all equilateral triangle faces.

A polyhedron with eight vertices that had more volume than any other eight-vertex shape previously known.” He adds: “It is ...

A triangle is a polygon. It is a closed 3-sided shape made up of straight lines ... angles in a triangle always add up to 180º. An equilateral triangle has 3 sides of equal length.