tetrahedron
A regular octahedron.
Octohedron, or diamond
A solid with 8 faces is an octahedron.As all faces are the same it is a regular octahedron.As such it is one of the five platonic solids - the only five 3D objects that can be regular: the tetrahedron (4 equilateral triangles for the faces), the hexahedron (usually called a cube with 6 square faces), the octahedron (as asked, 8 equilateral triangles for the faces), dodecahedron (12 regular pentagons as faces), icosahedron (20 equilateral triangles as faces).
An octahedron formed by joining together (base-to-base) two square-based pyramids.
tetrahedron
An octahedron.
What polyhedron has eight sides and all of the are equilateral triangle?
You're an octagon.
A regular octahedron.
A regular octahedron.
A regular octahedron.
Princess cut diamonds
pentagon
its a dedrehedron * * * * * Sadly, a dedrehedron does not exist. Fotunately, though, a regular octahedron does and it meets the specifications in the question.
that's easy its a triangle * * * * * That is such a nonsensical answer! A triangle is not even a polyhedron. The correct answer is an octahedron - two square based pyramids stuck together along their bases.
Octohedron, or diamond