# How can triangle inequlity be extended to become tetrahedron inequlity?

Since each side of a tetrahedron is a triangle is it possible to have an inequality that involves triangles that can form a tetrahedron?

• See answer to this question, it cover two cases where 1. only the lengths of 6 edges are given and 2. only the areas of 4 faces are given. Dec 18 '13 at 11:32

If you are asking "Find the necessary and sufficient condition that each of four positive numbers $a,b,c,d$ represents each area of the face of a tetrahedron", then it is known that the answer is $$a\lt b+c+d,b\lt a+c+d, c\lt a+b+d, d\lt a+b+c.$$