Week Sep28 - Oct4

    This week we learnt implication can be written in disjunction form according to implication law, and did some exercises on mixed quantifiers and began learning proof on friday's lecture. What I felt interesting is the implication rule and DeMorgan's law. Implication law says P => Q is equivalent to (not P) or Q. I thought about the relation between these two for a while and found if we say P => Q, we can say P is a subset of Q, but (not P) or Q doesn't mean the same thing, if we draw a Venn Diagram, we can see clearly the difference between these two. And distributive law, in Venn Diagram, P or (Q and R) is the same as (P or Q) and (P or R), but in real life, when we say Q and R, we can treat Q and R as a whole, let's say,T, so it is same to P or T, how can we say that P or (Q and R) is the same to (P or Q) and (P or R)?

   That was just my few thoughts about last week's lecture contents, I found it becomes more difficult but I will work harder.