I wonder if this statement
If disconnected set $A$ is union of two separated sets $B$, $C$, then $B$ $C$ are connected
is true or false? I try to construct counterexample on $\mathbb{R}$ but always have $B,C$ be connected.
Editted: I think I didn't state correctly in the first time, apologize for that
If $A$ is disconnected set, then it can always be written as union of connected separated sets
Try taking $A = (0,1) \cup (2,3) \cup (3,4) \cup (4,5)$?
For your edit: the comment below your question is helpful