Forgotten

October 21, 2014

Larry opened the lecture with an announcement that the assignment has been posted, but to manage our time, because Test 2 will take place the day after. I am glad he mentioned that, because I definitely forgot about it. Earlier, I took a peek at the assignment; it is all proofs (not that I was expecting anything else). I hope I can get comfortable with proofs before the assignment and test comes due…

As the lecture moved on to the next material (more proofs), I still am not sure, how much proof is enough? In PHL245, the tools to prove is limited, making the options limited and straightforward (if you can find the correct path). So far, the proofs in CSC165 could be endless, and less structured. Larry also mentioned there is a lot of practice questions that have been posted. I am planning to attempt those.

The second half of class was about Algorithms. Although the material was straightforward, it was interesting to see all the thoughts that is put into code I passively write for class.

Off to find time to practice,

Maya.

Proofs

October 14th, 2014

There’s no tutorial this week! I will be able to go home earlier to feed my dog!

In lecture, it was a continuation of proofs. Started with a simple example, which was very easy, and helped me understand the structure of a proof.

However, the professor re-introduced a formula:

>0, >0, x R, | x -2 |<, | x2-4 | <

I had a hard time coming to understand this, and only after the explanation was given, did I have any comprehension of it. Larry said to disregard the complicated-looking formula, and not be intimidated by the greek letters. But this is not about the greek letters! I may have mentioned in a previous sLog, but I am not confident I can solve this proof if something other than this question were to come up.

As we worked through this proof, I may or may not have understood. I can only hope that many many proofs will be done throughout this course, so I can finally say “I GET IT”.

As a side note, I am very impressed with the amount of people who received 100% on their first term test! Too bad I was not one of those, but still very impressed!!

Until next time,

Maya.

I PASSED

I PASSED
WOHOO

Term tests Augh

October 7, 2014

This week was the day of the first term test. When I was studying for the test, I used previous CSC165 term tests that I could find (2013). These tests had exercises that covered the material evenly. However, I felt there was not enough available exercises to practice with. I was still unsure as to what I did and did not understand 

Larry later sent out an e-mail with the previous term test. This was formatted differently, and covered the material in a different way than I have previously seen. Specifically, question #2 threw me off. There was a symbolized statement, and we had to prove which was correct, the initial statement or its negation. This was to test the understanding of quantifier sequences (e.g. difference between ∀ x, ∃ y versus there ∃ y, ∀ x). Sorting the logic out for this was confusing, so I decided to pop in for office hours. 

On Monday, there was a pleasant number of people who showed up, and proceeded like a mini classroom. Everyone had brought questions, and Larry explained to all of us the details of those answers. It helped me clarify a lot of different topics, and was very productive for me. 

When it came to actually writing the test, it had the same format as the term test Larry had sent out. This was when I was truly grateful I went to office hours. Had I worked on the old test alone, it would have been devastating, as my understanding was only vague. I tried to complete the test quickly, but I got stuck on the last question. It was hard to logically work through it, as the time was slowly running out. Only in the last five minutes I had figured out the answer. I quickly wrote an explanation, and before I can give an example, time had run out. Looking back, I realize, I did not give examples for most questions. I had explained in words; I really hope that is sufficient.

This week’s material followed the test, which was more or less about proofs. The first proof was very straightforward (infinite number of odd numbers), however, when Larry started with the infinite prime numbers proof, it started getting confusing. He was spewing on and on about P and Ks and factors. Ultimately, I was able to understand how the proof followed, however, if I am not confident I can solve a proof yet, if it was given to me to work through. Hopefully by next week, I will have a “Halleluah” moment, or maybe there’s more to proof than I think.

Hasta la vista,

Maya.

Proofs & Problem solving

September 30, 2014

This week’s lecture started with exercises on equivalencies with quantifiers, disjunctions, and conjunctions. Despite having worked on the first assignment this week, I had no idea how to find the answer. The first question was:

P=>Q is equivalent to:

A. ¬P ∨ Q

B. P ∨ ¬Q

C. P ∧ ¬Q

D. P ∧ Q

E. None of the above

I thought of the implication of this quantifier logically, but could not come to a conclusion. As he worked through the answer, it seems like this is less intuitive, and is only clear when the negative of this equation is worked out and compared to the already known equivalency. This exercised reminded me of the brief laws that were mentioned at the end of the previous class. I referenced week 3’s material in the next questions, and was then able to answer the questions. I was at a loss, because Larry had zoomed through the material (despite having a decent amount of time). It seemed like this material was not as important or will be covered in this week’s lecture, so I did not bother looking through these slides.

Looking through some of the theorems, they are very intuitive, but thinking of these formulas in a logical manner every time there was an equivalency question, seemed inefficient. So, I will probably straight off memorize the formulas.

Next thing that came up in class was sort of a fun surprise. Larry introduced it as a “real-life” proof. It was the hanging man paradox. To me, this was totally from left-field. The previous proof was a serious, down-to-Earth math question, but this question was a “neat-test-my-friends’-logic” kind of question. We did not have a lot of time to think this through, but the whole question is very interesting nonetheless, and I just might quiz my friends on it. If I was given the time, I wonder if I would be able to figure it out…

At the end of class, there was a folding exercise. I teamed up with a classmate named Jackie, and tried to work out the problem. Initially, trying to record the up and downs of the paper was very hard, as it kept flopping over, and had to keep the top and bottom consistent as we added more folds. After trying to re-record the folds many times, we started to be more familiar with the patterns. Initially, we looked at the sequences of up and downs. There were no apparent sequences. However, once  I thought of the problem logically (i.e. not in patterns, but focusing on what is actually happening to the paper), I had an “ah-ha!” moment. The paper is getting folded onto itself, and so the creases are happening between the previous crease. In addition, if there is a fold on the one side, there must be another fold on the other side that fits in with the fold. So if we start of with our initial sequence, if we space it out, and as long as we can fill in the inbetween of one side, the other will be simple! I had thought it would simply be one UP fold on the other, while the other was DOWN. Happily satisfied with my answer, I waited for Larry’s real answer.

As you know, there is a slight flaw to my answer, as all the creases on one side do not become just one kind of fold. Almost there, but not quite there. Regardless, the exercise was very engaging and enjoyable.

In this week’s tutorial, Grace very graciously answered my “dur” questions. Thanks again!

Until next time,

Maya.