why the triangular based pyramid is called a pyramid
A triangular pyramid is a pyramid having a triangular base. The tetrahedron is a triangular pyramid having congruent equilateral triangles for each of its faces. where is the height and is the length of a side of the base. where is the area of the triangular base and is the height of the pyramid. The regular tetrahedron is a special case of the triangular pyramid. From MathWorld--A Wolfram Web Resource.