CSC165 SLOG Week4

What’s something new I learned this week?

1、Transitivity

(P ⇒ Q)∧ (Q⇒ R) ⇒(P ⇒ R)

2、Double Quantifiers

Free to switch the order of quantifiers, does not change the meaning.The order in which we consider elements of an ordered pair doesn't change the logic.

3、A proof foretold

1. Understand why you believe the thing is true. This step is

messy, creative, but then increasingly precise to identify

(and then strengthen) the weak parts of your belief.

2. Write up (express) why you believe the thing is true. Each

step of your written proof should be justied enough to

convince a skeptical peer. If you detect a gap in your

reasoning, you may have to go back to step 1.

4、Chains with ∧or ∨

(P⇒R1)∧(P⇒R2 ) ⇔ (P ⇒ (R1∧R2))

((R1⇒ Q)∧(R2 ⇒Q)) ⇔((R1∨R2) ⇒Q)

How did your tutorial/test/assignment go this week?

 For tutorial, I learned that "A and B are both guarantees that C is true. " means (A ∨ B ⇒ C),not means A ∧ B ⇒ C.
 And for assignment1 this week, I learned that
 1)the converse of the contrapositive of the imlpication, is the same as the convere of the implication.
 2) "necessary and sufficient" means "⇔"  
 3) " A ⇒ C" is true means A can imply C.