Question 1029233
P(A_or_B)=P(A)+P(B)-P(A_and_B)
So for complements,
P(A_or_Ac)=P(A)+P(Ac)-P(A_and_Ac)
However by definition of complement,
P(A_and_Ac)=0
So,
P(A_or_Ac)=P(A)+P(Ac)
P(A_or_Ac)=1
So for example, probability that it will rain or that it won't rain is 100%. _