# Equilateral-triangles sentence example

equilateral-triangles

- If the faces be all equal equilateral triangles the solid is termed the "regular" tetrahedron.
- If three equilateral triangles be placed at a common vertex with their covertical sides coincident in pairs, it is seen that the base is an equal equilateral triangle; hence four equal equilateral triangles enclose a space.
- In a similar manner, four covertical equilateral triangles stand on a square base.
- Five equilateral triangles covertically placed would stand on a pentagonal base, and it was found that, by forming several sets of such pyramids, a solid could be obtained which had zo triangular faces, which met in pairs to form 30 edges, and in fives to form 12 vertices.