HI , I dont know where to post my question. sorry if it is not in the correct forum. I am working on a program and one of the instruction say this: (Prior we have to know that a,b,c are the sides of a triangle) "Note that not all combination of a,b,c produce a triangle. Your function should produce correct results for legal data and reasonable results for illegal combinations" I did not know that there can be bad combination for a triangle. What is this bad combination? thank you B.