diff --git a/exercises/triangle/description.md b/exercises/triangle/description.md index 6de895b835..791e96c282 100644 --- a/exercises/triangle/description.md +++ b/exercises/triangle/description.md @@ -2,6 +2,27 @@ The program should raise an error if the triangle cannot exist. ## Hint -The sum of the lengths of any two sides of a triangle always exceeds or -is equal to the length of the third side, a principle known as the _triangle -inequality_. +The triangle inequality theorem states: +z ≤ x + y +where x,y, and z are the lengths of the sides of a triangle. In other words, the +sum of the lengths of any two sides of a triangle always exceeds or is equal to +the length of the third side. + +A corollary to the triangle inequality theorem is there are two classes of +triangles--degenerate and non-degenerate. If the sum of the lengths of any two +sides of a triangle is greater than the length of the third side, that triangle +is two dimensional, has area, and belongs to the non-degenerate class. In +mathematics, a degenerate case is a limiting case in which an element of a class +of objects is qualitatively different from the rest of the class and hence +belongs to another, usually simpler, class. The degenerate case of the triangle +inequality theorem is when the sum of the lengths of any two sides of a triangle +is equal to the length of the third side. A triangle with such qualities is +qualitatively different from all the triangles in the non-degenerate class since +it is one dimensional, looks like a straight line, and has no area. Such +triangles are called degenerate triangles and they belong to the degenerate +class. + +## Dig Deeper + +This exercise does not test for degenerate triangles. Feel free to add your own +tests to check for degenerate triangles.