A parallelogram.
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.
tetrahedron
Isosceles TetrahedronA solid with four faces is a tetrahedron. Each of the faces is a triangle. If all the triangles are congruent, you have an isosceles tetrahedron.
Four equilateral triangles make up another equilateral triangle.
A tetrahedron has four equilateral triangles as sides
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.
A parallelogram.
square
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.
Fuor toothpicks from 16 leave 12 which, by coincidence (?) is exactly enough for four equilateral triangles!
Rohmbus is a four sided figure (quadrilateral) that is made up of two equilateral triangles
Types of Triangles: By Sides: Isosceles- 2 congruent sides Scalene- no congruent sides Equilateral- 3 congruent sides By Angles: Acute- angles measuring less than 90° Obtuse- one angle measuring more than 90° Right- one angle measuring exactly 90° Equiangular- all angles measuring exactly the same- same as equilateral triangle
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.
tetrahedron
Put four equilateral triangles so that each one of them has a vertex at a single point and the triangles abut one another. The shape will be 4/6 (= 2/3) of a regular hexagon.
Isosceles TetrahedronA solid with four faces is a tetrahedron. Each of the faces is a triangle. If all the triangles are congruent, you have an isosceles tetrahedron.