The OP was asking about dihedral. You made assumptions about his question that makes his question irrelevant. The others here are making assumptions, or adding information, that keeps his question relevant. I think the second set of assumptions are more reasonable, don't you? Or do you really think the OP will be satisfied with the answer "it doesn't"? Don't you think he is after information about dihedral, and that providing situations where dihedral is relevant is a better way to answer?