서론중간고사를 봐야해요...중요한 정리들을 정리하겠습니다.갖다놓고 외워봅시다.본론1. Definition of $\pi$, $\lambda$ system1) $\pi$ systemA collection $P$ is a $\pi$-system if for $A,B \in P$, $A \cap B \in P$ 2) $\lambda$ systemA collection $L$ is a $\lambda$-system if- $\emptyset \in L$- If $A^c \in L$, $A \in L$- If$A_1,A_2,... \in L$ and $A_1,A_2,...$are disjoint, then $\bigcup_{k=1}^{\infty} A_k \in L$ 2. $\pi$, $\lambda$ syste..
