
Discrete Mathematics
Assignment#02
1. Use truth tables to determine whether the argument form is valid:
p∨q
p−→∼ q
p−→ r
∴r
2. Use symbols to write the logical form of each argument. If the argument is valid, identify
the rule of inference that guarantees its validity. Otherwise, state whether the converse
or the inverse error is made.
a)
If Jules solved this problem correctly, then Jules obtained the answer 2.
Jules obtained the answer 2.
∴Jules solved this problem correctly.
b)
This real number is rational or it is irrational.
This real number is not rational.
∴This real number is irrational.
3. A set of premises and a conclusion are given. Use the valid argument forms to deduce
the conclusion from the premises, giving a reason for each step. Assume all variables are
statement variables.
4. Find the truth set of each predicate.
a) predicate: 6/d is an integer, domain: Z
c) predicate: 1 ≤x2≤4, domain: R
5. Let the domain of x be the set D of objects discussed in mathematics courses, and let
Real(x) be “x is a real number,” Pos(x) be “x is a positive real number,” Neg(x) be “x
is a negative real number,” and Int(x) be “x is an integer.”
a. ∀x, Real(x)∧N eg(x)−→ P os(−x).
b. ∃xsuch that Real(x)∧ ∼ Int(x).