I was studing about the monogamy. Then I saw this phrase
$$C_{AB}^2 + C_{AC}^2 ≤ C_{A(BC)}^2$$ where $C_{AB}, C_{AC} $ are the concurrences between A and B and between A and C respectively, while $C_{A(BC)}$ is the concurrence between subsystems A and BC.
I know what the the concurrence of a bipartite system is, I just dont know how to calculate $C_{A(BC)}$, that is the concurrence between subsystems A and BC. How I do this?
