MATH255 - Mid Term Exam Flashcards
What is a statement
An expression that is either true or false, without ambiguity.Example: “I am a man”
What is a True Statement
Definition: A logically valid statement that is true.Example: “3 + 4 = 7”
What is a Not Statement
Definition: A statement negated using the “~” symbol.Example: “~(3 + 4 = 7)”
What is Ambiguity
Definition: Lack of clarity or uncertainty in a statement.Example: “x > 2” (ambiguous because it depends on the value of x)
What is There exists
Definition: Indicates the existence of at least one element satisfying a condition.Example: “There exists x such that x < 2”
What is a False Statement
Definition: A logically invalid statement that is false.Example: “If x^2 = 9, then x = 1 or x = -1”
What is a Conjunction
Definition: A logical operation that combines two statements into a single statement, true only if both original statements are true.Example: “It is raining outside” ^ “I am wearing a raincoat”p ^ q “and”
What is a Disjunction
Definition: A logical operation that combines two statements into a single statement, true if at least one of the original statements is true.Example: “I take the bus to school” v “I take the train to school”p v q “or”
What is a Conditional
Definition: A statement that implies that if one condition is met, another condition must also be met.Example: “If I work hard, then I do well.”p > q “implies”
What is a Tautology
Definition: A compound statement that is always true, regardless of the truth values of its components.Example: “p v ~p”
What is a Fallacy
Definition: A compound statement that is always false, regardless of the truth values of its components.Example: “p ^ ~p”
What is a Biconditional
Definition: A statement that implies two conditions are equivalent.Example: “x^3 = -8” <-> “x = -2”p <-> q “p implies q, but also q implies p”
What is Equivalence Laws
Definition: A set of logical laws that describe how logical operators interact with each other.Example: Commutative, Associative, Distributive, etc.
What is a Contingency
Definition: A statement that is sometimes true and sometimes false, neither a tautology nor a fallacy.Example: “p ^ q”
What is Equivalence
Definition: Two statements are logically equivalent if they have identical truth table values.Example: “p ≡ ~(~p)”
What is Substitution Rule
Definition: If in a tautology all instances of a variable are replaced by the same statement, it remains a tautology.Example: p^~p turns into q^~q
What is Distributive Laws
Definition: Laws stating how one operation distributes over another.Example: p ∨ (q ∧ r) ≡ (p ∨ q) ∧ (p ∨ r)
What is Associative Laws
Definition: Laws stating that the grouping of operands does not change the result.Example: (p ∨ q) ∨ r ≡ p ∨ (q ∨ r)
What is Commutative Laws
Definition: Laws stating that the order of operands does not change the result.Example: p ∨ q ≡ q ∨ p
What is Double Negation Law
Definition: The negation of a negated statement.Example: ∼∼ p ≡ p
What is De Morgan’s Laws
Definition: Laws describing how negation distributes over logical operators.Example: ∼(p ∨ q) ≡ ∼p ∧ ∼q
What is Implication Laws
Definition: Laws relating to conditional statements.Example: p ↔ q ≡ (p → q) ∧ (q → p)
What is Main Connective
Definition: The primary logical operator in a compound statement that binds it together.Example: In (p ∨ q) → (r ∧ s), “→” is the main connective.
What is Universal Quantifier
Definition: Symbolized as ∀, it means “For all.” Used in predicate logic to denote that a statement applies to all elements in a given domain.Example: ∀x ∈ D, p(x) means “For all x in the domain D, p(x) is true.”
What is Existential Quantifier
Definition: Symbolized as ∃, it means “There exists.” Used in predicate logic to indicate that there is at least one element in a given domain for which a statement is true.Example: ∃x ∈ D, p(x) means “There exists an x in the domain D for which p(x) is true.”
What is Predicate
Definition: A variable statement that evaluates to true or false when specific values are substituted for its variables.Example: p(x): “x is an integer less than 5”
What is Universal Quantifier Example
Definition: An example illustrating the use of the universal quantifier (∀) in a statement.Example: ∀x ∈ D, p(x) means “For all x in the domain D, p(x) is true.”
What is Domain
Definition: The set of all possible values that can be substituted into a predicate.Example: Domain of p is Z (the set of all whole numbers).
What is Truth Set
Definition: A subset of the domain that contains the elements for which the predicate is true.Example: Truth set of p(x) contains {-2, -1, 0, 1, 2, 3, 4}.
What is Existential Quantifier Example
Definition: An example demonstrating the use of the existential quantifier (∃) in a statement.Example: ∃x ∈ D, p(x) means “There exists an x in the domain D for which p(x) is true.”
What is Negation of Existential Statement
Definition: The process of negating an existential statement to make it a universal statement.Example: ~∃x ∈ Z, x is even becomes ∀x ∈ Z, x is not even.
What is Negation of Universal Statement
Definition: The process of negating a universal statement to make it an existential statement.Example: ~∀x ∈ R, x > 0 becomes ∃x ∈ R, x ≤ 0.
What is Direct Proof
Definition: A method of proof that starts with given assumptions and progresses in a forward manner to reach a conclusion.Example: Proving that if 3x - 9 = 15, then x = 8.
What is Modus Ponens
Definition: A valid form of argument where if you have a conditional statement “If p, then q” and you know p is true, you can conclude that q is true.Example: If p, then q; p; ∴ q.
What is Proof by Contradiction
Definition: A proof technique that assumes the opposite of what needs to be proved, and then shows that this assumption leads to a contradiction, thus establishing the original statement’s truth.Example: Proving that for all n ∈ N, if n^2 is even, then n is even, by contradiction.
What is Modus Ponens Example
Definition: An example illustrating the use of Modus Ponens in a logical argument.Example: If it’s raining (p), then I will bring an umbrella (q); It’s raining (p); ∴ I will bring an umbrella (q).
What is Law of Syllogism
Definition: A valid form of argument where if you have two conditional statements “If p, then q” and “If q, then r,” you can conclude “If p, then r.”Example: If p, then q; If q, then r; ∴ If p, then r.
Law of Syllogism Example
Definition: An example illustrating the use of the Law of Syllogism in a logical argument.Example: If I study (p), I will pass the exam (q); If I pass the exam (q), I will graduate (r); ∴ If I study (p), I will graduate (r).
What is Law of Contrapositive
Definition: A valid form of argument that states if you have a conditional statement “If p, then q,” the contrapositive statement “If ~q, then ~p” is also true.Example: If p, then q; ∴ If ~q, then ~p.
What is Law of Contrapositive Example
Definition: An example demonstrating the use of the Law of Contrapositive in a logical argument.Example: If it’s a square (p), then it has four sides (q); ∴ If it doesn’t have four sides (~q), then it’s not a square (~p).
What is Negation mean
~
What is Conjunction mean
What is Disjunction mean
v
What is Conditional mean
->
What is Biconditional mean
<->
What is ~
Negation
What is ^
Conjunction
What is v
DIsjunction
What is ->
Conditional
What is <->
Biconditional