A four sided figure would be a tetrahedron and a 20 sided would be an icosahedron. They both have equilateral triangles for faces so your question is a little incomplete.
Differences: Squares have 4 sides / equilateral triangles have 3 sides. Squares have 90 degree angles / equilateral triangles have 60 degree angles. Squares have 2 diagonals / equilateral triangles have none Similarities: All sides of the shape are congruent All angles of the shape are congruent
Some triangles are symmetric, while others are not. All equilateral and isosceles triangles are symmetric.all triangles are symmetric.
A triangle based pyramid.
The tetrahedron has 4 equilateral triangles as its faces.
This shape is called a Icosahedron , I think.
An octahedron is a 3d shape that has eight faces. An octahedron is made from equilateral triangles, with four points meeting in one spot called a vertex.
That shape is a unit equilateral triangular dipyramid, and it has 6 faces.
A three-dimensional figure or shape, such as a tetrahedron, has four faces. These faces are equilateral triangles. A tetrahedron also has four vertices and 6 edges.
A three-dimensional shape with eight triangular faces is called an octahedron.
An icosahedron is a shape with twenty equilateral triangles as faces.
In geometry, an octahedron (plural: octahedra) is a polyhedron with eight faces. A regular octahedron is a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex.It is a 3-dimensional cross polytope (shape).---Wikipedia
A four faced figure is a tetrahedron. If they are all congruent triangles, they are all equilateral triangles and it is a regular tetrahedron - one of the 5 Platonic Solids.
An octahedron is a closed 3-d shape with 8 polygonal faces. There are 257 topologically different convex octahedra. The faces of octahedra can be triangles, quadrilaterals, pentagons, hexagons or heptagons. There are many examples of octahedra - a hexagonal prism, for example - which has no triangular face. At the other extreme, all the faces of a regular octahedron are equilateral triangles.