S1, C2: Logic

Question 1

Converse

Answer 1

The converse of A => B is B => A.

Question 2

Equivalence

Answer 2

P is equivalent to Q if P is true iff Q is true. P Q.

Question 3

Negation

Answer 3

The negation of P is ¬P (not P).

Question 4

Contrapositive

Answer 4

The contrapositive of P => Q is ¬Q => ¬P. These two statements are equivalent.

Question 5

The statement P => Q is equivalent to

Answer 5

¬P ‘or’Q

Question 6

Injective

Answer 6

A function f: A -> B is injective if for all s, t ∈ A s.t. s =/ t, then f(s) =/ f(t).

Question 7

Surjective

Answer 7

We say that f is surjective if, for each b ∈ B, there

exists at least one element a ∈ A such that f(a) = b.