A tetrahedron is an example of a triangular pyramid. Every face is a triangle, and each face touches every other face on one edge.
Consider a "unit cube", with all edges equal to 1 inch in length. Eight vertices - A, B, C, D, clockwise around the top, E, F, G, H on the bottom, with A directly above E, B directly above F, etc. Triangle Type 1 is completely confined to one face of the cube. The second and third points are adjacent (connected by an edge of the cube) to the first, but are opposite each other, but still on the same face. Two of the sides are edges of the cube, and therefore have a length of 1 inch. The third side is a diagonal drawn across one face of the cube, and has a length of √2 inches. This is a right triangle, and is also an isosceles triangle (the two sides adjacent to the right angle have the same length). The area of this triangle is 1/2 square inch. A typical triangle of this type is ABC. Triangle Type 2 has two vertices that are adjacent to each other (on the same edge of the cube), but the third point is the opposite vertex of the cube from the first point, and is the opposite vertex on the same face as the second point. One side is an edge of the cube and has a length of 1. The second side is a diagonal drawn across one face of the cube, and has a length of √2. The third side is a diagonal drawn between opposite vertices of the cube, and has a length of √3. This is also a right triangle, but not an isosoceles triangle, and therefore different from the first type. The area of this triangle is √2/2. A typical triangle of this type is ABG. Triangle Type 3 has three vertices that are opposite each other along the same face (though on three different faces). I.e., Vertices 1 and 2 are opposite each other along one face, 2 and 3 are opposite each other along another face, and 1 and 3 are opposite each other along a third face. All three sides have a length of √2. This is an equilateral triangle. The area of this triangle is √3/2. A typical triangle of this type is ACF.
Octogon
Yes it is a tetrahedron
Well, honey, you're gonna need 20 short isosceles triangles to build that fabulous Icosahedron. Each face of the Icosahedron is made up of an isosceles triangle, and there are 20 faces in total. So, do the math and get building, darling!
Each face is an equilateral triangle.
One face that is the equilateral triangle.One face that is the equilateral triangle.One face that is the equilateral triangle.One face that is the equilateral triangle.
A tetrahedron is a four sided polyhedron. Each face is a triangle. If it is a regular tetrahedron, then each face is an equilateral triangle.
A regular octahedron is one of the platonic solids. Each of its faces is an equilateral triangle.
None. Each face is an equilateral triangle.
equilateral triangle
An equilateral triangle.
The figure described is a polyhedron. It is a tetrahedron known as a triangular pyramid.
Equilateral
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.
If its a triangular based pyramid (tetrahedron) then it will have 4 equilateral triangle faces and so find the area of one face and multiply it by 4 to give the total surface area.
A triangle has 3 vertices and three sides (edges). It has one face.