Journal 2 - Week 3

Friday   September.26th, 2014   Sunny

       This week, Professor introduces Conjunction and Disjunction to us. Conjunction and Disjunction are both used to connect statements. However, they "combine" the statements in quite different ways.

For the statements combined by conjunction, the whole sentence is true only when all of the statements are true. If any one of them is false, even though the others are true, the whole sentence is still false. For the statements connected by disjunction, the requirement for the whole sentence to be true is that at least one of the statements is true. It will be false only when all the statements are false.

This makes conjunction and disjunction sound like the English word "and". Indeed, conjunction is a logical "and", but the English word "and" is sometimes different. English causes ambiguity, the examples can be found in Professor's ppt material. The "inclusive" and "exclusive" example is pretty good.

A difficult part for me of this week is De Morgan's Law. At first, I cannot understand this law, so I just try to memorize it. This leads to the fact that I spent much time in doing exercises because I need to think a lot even in very basic question. For dealing with this problem, I carefully read our online notes. According to the guide, I drew some Venn diagrams about different expressions. After drawing Venn diagrams, I clearly saw that the same meaning can be expressed by different ways. This helps me deeply understand De Morgan's Law and is also very helpful for me to use conjunction and disjunction.

At the end, I just want to remind that assignment 1 will be due in very soon. Hopefully everyone gets a good mark.

See you next week :)

Cecilia

Journal 1 - Week 1 & Week 2

Friday   September.19th, 2014   Sunny 

       Hello my great audiences! Much appreciated for sharing your time to read my journal. 

       Week 1 helps us understand the importance of precision. Language is a very useful and common way people use to communicate with each other. However, human language, including the words from our tongue and sentences written on papers, usually creates ambiguity at the same time that express ideas. This is why we need to learn about the mathematical expression and focus on computer language in this course. 

       From Week 2, I learn that "an argument is true when it is impossible for the antecedent is true and conclusion false". An interesting point we can get from this sentence is that a false premise implies anything because the situation that a true antecedent and a false conclusion appear at same time will never happen. On the other side, we can think both antecedent and conclusion as sets. We can only get an empty set according to a false antecedent. When the premise is false, the whole sentence would be true whatever the conclusion is true or false because empty set can be a subset of any set.

       At the end of my journal, I suggest everyone to read my TA's blog (http://myricecrispi.wordpress.com). She talks a lot about how to be successful in CSC165. Notice that one of the most important contents of CSC165 is Mathematical proof. If you haven't taken any math course before, please pay attention to this part. 

See you next week :)

Cecilia