pentagon
What polyhedron has eight sides and all of the are equilateral triangle?
An octahedron.
tetrahedron
You're an octagon.
A regular octahedron.
A regular octahedron.
Princess cut diamonds
Octohedron, or rhomboid.
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.
its a dedrehedron * * * * * Sadly, a dedrehedron does not exist. Fotunately, though, a regular octahedron does and it meets the specifications in the question.
A regular octahedron.
An octahedron formed by joining together (base-to-base) two square-based pyramids.