slog for CSC165 week3

  This week we learnt some useful symbols and ways of expressions for CSC165. I have known that "unless" can be translated into "if not".And I can finally tell the difference between the symbol of conjunction and symbol of implication and how to use them under different circumstances. Conjunction is referred to "and" in English and disjunction is referred to "or".I also learnt negation. If a statement is true, then its negation must be false. The symbol of universal quantification and existence quantification can be changed into each other by the way of negation, which is a convenient method.In addition, I learnt that drawing venn diagram is not the only way to translate an expression. We can also use tabulating truth by drawing a table with T and F, which is more easily to understand. Moreover,tautology means the statement is true in every possible world. We call a statement satisfiable if it is sometimes true while we call it unsatisfiable if it is never true. There is an interesting law called De Morgan's Law which switch the roles of the symbol of conjunction and disjunction as with magic.In the last class this week, we played a game by folding a strip for several times. Firstly, I found it very difficult cause I have no idea. After several minutes of thinking I figured out how to get started.During that progress, I found the regular pattern gradually and can predict the sequence of ups and downs. It is so funny.
  Next week we will have the first CSC165 test. I wish I can do it well.