Write each of the following three statements in symbolic form and determine which pairs are logically equivalent. Include truth tables and a few words of explanation. If it walks like a duck and it talks like a duck, then it is a duck.

Either it does not walk like a duck or it does not talk like a duck, or it is a duck.

If it does not walk like a duck and it does not talk like a duck, then it is not a duck.

If it walks like a duck and it talks like a duck, then it is a duck.

and

Either it does not walk like a duck or it does not talk like a duck, or it is a duck.

are logically equivalent to each other.

but neither of the two is logically equivalent to

If it does not walk like a duck and it does not talk like a duck, then it is not a duck.

Step-by-step explanation:

Given statements:

Statemen 1:

If it walks like a duck and it talks like a duck, then it is a duck.

Statement 2:

Either it does not walk like a duck or it does not talk like a duck, or it is a duck.  

Statement 3:

If it does not walk like a duck and it does not talk like a duck, then it is not a duck.

Let

Using p = it walks like a duck , q =it talks like a duck, r = it is a duck  the given statements can be written in symbolic form as:

Statement 1:  

p ∧ q → r

The ∧ symbol shows that if both p and q are true then, they imply r. This means both p and q together imply r

Statement 2:

~p ∨ ~q ∨ r

Here the statement p and q are negated and joined using or. So either negation p or negation of q or r (alternative)  

Statement 3:

~p ∧ ~q → ~r

The ∧ symbol shows that if both negation of p and negation of q are true then, they imply r. This means both negated p and negated q together imply negated r

Statement 1:

p ∧ q → r ≡ ~(p∨q) ∨ r               Using conditional equivalence p→q ≡ ~p ∨ q

              ≡ (~p ∧ ~q ) ∨ r          

You can see it is  equivalent to Statement 2 i.e. ~p ∧ ~q → ~r

Hence Statement 1 and Statement 2 are logically equivalent.

Now Statement 3:

~p ∧ ~q → ~r ≡ ~(~p ∧ ~q ) ∨ ~r   Using conditional equivalence p→q ≡ ~p ∨ q

                     ≡ ~(~p ) ∨ ~(~q ) ∨ ~r Using De Morgan's Law ~(p∧q) ≡ ~p ∨~q

                     ≡  p ∨ q ∨ ~r Using Double Negation Law ~(~p)≡p

This shows that Statement 3 is neither logically equivalent to Statement 1 nor logically equivalent to Statement 2.

Proof by truth table is attached. The table shows that the columns for Statement 1 and Statement 2 have same truth values.

Hence

"If it walks like a duck, and it talks like a duck, then it is a duck,"

and

"If it does not walk like a duck, and does not talk like a duck, then it is not a duck,"

are logically equivalent.

The table also shows that column for Statement 3 does not match with either of the columns for Statement 1 and Statement 2. So

If it does not walk like a duck and it does not talk like a duck, then it is not a duck.

is not logically equivalent to Statement 1 and Statement 2.

a triangular prism is a 3 dimensional shape composed of triangles and rectangles. it is made from two triangular bases and three rectangular sides.