Triangle inequality theorem

The Triangle Inequality Theorem states that in any triangle, the length of any one side must be less than the sum of the other two sides and greater than their difference. This means you cannot have a triangle where one side is as long as or longer than the combined lengths of the other two sides, because then it wouldn't close properly. For example, if one side is 8 units, the other two must add up to more than 8 but not less than their difference for the triangle to exist. It ensures the sides can connect to form a proper triangle.