Two regular tetrahedrons connected face to face make a "regular triangular dipyramid."
That is one of the 92 "Johnson solids." Those are the convex polyhedrons whose faces are regular polygons but do not belong to either of the two sets of highly symmetric polyhedrons (the Platonic and the Archimedean) or to the perhaps less interesting two infinite families of prisms and antiprisms.
If the two tetrahedrons overlap, both centers at the same place but with the tetrahedrons facing in opposite directions, it makes a "stellated octahedron."
Chat with our AI personalities
an octahedron: basically two square based pyramids with their bases stuck together.
Two angles which added together make 90o are called Complementary angles
It look like two square based pyramids stuck together on their square sides.
A regular triangular dipyramid. It is one of the 92 "Johnson solids". Those are the convex polyhedra whose faces are regular polygons, but do not belong to either of the two sets of highly symmetric polyhedra (the Platonic and the Archimedean), or to the perhaps less interesting two infinite families of prisms and antiprisms.
A triangular bipryramid (two triangular pyramids stuck together on one face), a parallelepiped (like a squished cuboid), a pentagonal pyramid. A cube or rectangular prism are special cases of a parallelepiped.