# Show that if a node $u$ is joint of a graph $G$ then its not a joint of $G^c$ (complement of $G$)

I know that a joint $$u$$ means that if $$G - u$$ then $$G$$ isnt connected anymore, but i dont know how to use that definition in order to reach the proof. The proposition makes logical sense given the definition of the complement of $$G$$ but i dont even know how to start

• If a joint vertex is the same as a cut vertex, then this question has an excellent answer here. Sep 27 '21 at 9:15