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MATH211-Exam1
Term | Definition |
---|---|
(definition) universal statement | Says that a certain property is true for all elements in a set. |
(definition) conditional statement | Says that if one thing is true then some other thing is also true. |
(definition) existential statement | Says that there is at least one thing for which some property is true. |
universal statement form | "For all..." |
conditional statement form | "If..., then..." |
existential statement uses form | "There exists..." |
(definition) universal conditional statement | A statement that is both universal and conditional |
universal conditional statement form | "For all _____(set), if _____(check property), then _____(property to follow)." |
(definition) universal existential statement | A statement that is universal because its first part says that a certain property is true for all objects of a given type, and it is existential because its second part asserts the existence of something. |
universal existential statement form | "For all _____(set), there is _____(property/object specific)." |
(definition) existential universal statement | A statement that is existential because its first part asserts that a certain object exists and is universal because its second part says that the object satisfies a certain property for all things of a certain kind. |
existential universal statement form | "There exists _____(object in set), such that for all _____(set), _____(property)." |
(definition) logic | The study of reasoning; it is specifically concerned with whether reasoning is correct. |
(definition) argument | A sequence of statements aimed at demonstrating the truth of an assertion. |
conclusion | The assertion at the end. |
premises | Statements leading to an assertion. |
(definition) statement/proposition | A sentence that is true or false but not both. The truth value is TRUE if it is true and FALSE if it is false. |
negation of p | Means "not p" or "it is not that case that p" |
negation of p denotion | ~p |
the conjunction of p and q | Means "p and q" |
the conjunction of p and q denoted | p ∧ q |
the disjunction of p and q | Means "p or q" |
the disjunction of p and q denoted | p ∨ q |
(definition) logical equivalence | Statement forms that have identical truth values for each possible substitution for their statement variables. |
logical equivalence denoted | P≡Q |
De Morgan's Laws (a) | ~(p ∧ q) ≡ ~p ∨ ~q |
De Morgan's Laws (b) | ~(p ∨ q) ≡ ~p ∧ ~q |
(definition) tautology | A statement that is always true. |
(definition) contradiction | A statement that is always false. |
(definition) conditional statements | "if p then q" |
conditional statements denoted | p --> q (p is the hypothesis, q is the conclusion) |
(definition) vacuously true | A conditional statement that is true by virtue of the fact that its hypothesis is false. |
(theorem) p → q ≡∼ p∨q | (theorem) The statement “if p then q” is logically equivalent to “not p or q.” |
(theorem) ~(p → q) ≡ p ∧ ~q | (theorem) The negation of “if p then q” is logically equivalent to “p and not q”. |
(definition) contrapositive of p --> q | ~q --> ~p |
(theorem) p --> q ≡ ~q --> ~p | (theorem) A conditional statement is logically equivalent to its contrapositive. |
(definition) converse of p --> q | q --> p |
(definition) inverse of p --> q | ~p --> ~q |
(definition) "p only if q" means... | "if not q then not p." / "if p then q" |
Order of operations for logical operators | 1. ~ [negations first] 2. ∧, ∨ [evaluate ∧ ∨ second, parentheses may be needed] 3. -->, <--> [evaluate -> and <--> third, parentheses may be needed] |
(definition) sufficient condition | If r and s are statements: r is a sufficient condition for s means “if r then s.” r is a necessary condition for s means “if not r then not s” or “if s then r.” |
(definition) syllogism | An argument form with two premises and a conclusion. |
modus ponens | p-->q p ∴q |
modus tollens | p-->q ~q ∴~p |
rule of inference | A form of argument that is valid. |
generalization | A valid argument form. p ∴ p∨q q ∴ p∨q |
specialization | A valid argument form. |
elimination | p ∨ q ~q ∴ p p ∨ q ~p ∴ q |
transitivity | p --> q q --> r ∴ p --> r |
Proof by Division into Cases | p ∨ q p --> r q --> r ∴ r |
Contradiction Rule | If you can show that the assumption that statement p is false leads logically to a contradiction, then you can conclude that p is true. ~p --> c ∴ p |
(definition) fallacy | An error in reasoning that results in an invalid argument. |
converse error | An invalid argument form. p --> q q ∴ p |
inverse error | An invalid argument form p-->q ~p ∴ ~q |
(definition) predicate | A sentence that contains a finite number of variables and becomes a statement when specific values are substituted for the variables. |
(definition) domain | The set of all values that may be substituted in place of the predicate variable |
Method of Exhaustion | When a domain is finite, a technique for showing that a universal statement is true. |
(definition) existential statement | A statement of the form “There is an x in the domain such that Q(x)." It is defined to be true if, and only if, Q(x) is true for at least one x in D. It is false if, and only if, Q(x) is false for all x in D. |
universal conditional statement | "For all of x, if P(x) then Q(x)." |
(theorem) Negation of a Universal Statement | "For all x in D, Q(x) is true" to "There exists an x in D such that Q(x) is not true." |
(theorem) Negation of an Existential Statement | "There exists an x in D such that Q(x) is true." to "For all x in D, Q(x) is false." |
(theorem) Negation of a Universal Conditional Statement | "For all of x, if P(x) then Q(x)." to "There exists an x such that P(x) and ~Q(x)." |
Sufficient condition for "For all of x, if r(x) then s(x)." | "For all of x in r(x)." |
Necessary condition for " ~if r(x) then ~s(x)." | "For all of x in r(x)." |
Only if for "~s(x) then ~r(x)." | "For all of x in r(x)." |
Rule of Universal Instantiation | If some property is true of everything in a domain, then it is true of any particular thing in the domain. |
Universal Modus Ponens | (Universal Instantiation) ∀x, if P(x) then Q(x) [<--major premise] P(a) for a particular a [<-- minor premise] ∴ Q(a) |
Universal Modus Tollens | ∀x, if P(x) then Q(x) ~ Q(a) for a particular a ∴ ~P(a) |
Universal Transitivity | ∀x, P(x) --> Q(x) ∀x, Q(x) --> R(x) ∴ ∀x, P(x) --> R(x) |
Converse Error | ∀x, if P(x) then Q(x) Q(a) for a particular a ∴ P(a) |
Inverse Error | ∀x, P(x) --> Q(x) ~P(a) for a particular a ∴ ~Q(a) |