推广:1)P(A4∪A∪UA)=P(A)+P(A2)+P(A3) P(A1A2)-P(A2A3)-P(A1A3) +P(A4243) 2)P(A1UA2U…UA) ∑P(4)∑P(44)+ 1≤i,j≤n +(-1)P(A1A2…An)2) = − + = ≤ ≤ ∑ ∑ P Ai P A A i n i j n i j ( ) ( ) 1 1 , L + − − ( )1 ( ) 1 1 2 n P A A L An P A A An ( ) 1 2 U ULU 推广： 1) − P A( ) A − P(A A ) − P A( A ) 1 2 2 3 1 3 + P A( ) 1 2 A A3 P A( ) A A P A( ) P A( ) P A( ) 1 2 U U 3 = 1 + 2 + 3