[tex]\it E\in(EAC)\ \c{s}i\ E\in(EBD) \Rightarrow E\in(EAC)\cap(EBD)\ \ \ \ \ (1)\\ \\ Not\breve am\ AC\cap BD=\{O\}\\ \\ O\in AC\ \c{s}i\ AC\subset(EAC) \Rightarrow O\in(EAC)\ \ \ \ \ (2)\\ \\ O\in BD\ \c{s}i\ BD\subset(EBD) \Rightarrow O\in(EBD)\ \ \ \ \ (3)\\ \\ (2),\ (3) \Rightarrow O\in(EAC)\cap(EBD)\ \ \ \ \ (4)\\ \\ (1),\ (4) \Rightarrow (EAC)\cap(EBD)=EO[/tex]
