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Discrete Structures
Exam 1
| Question | Answer |
|---|---|
| Statement/Proposition | A sentence that’s T/1 or F/0 - ABC: Letters that represents Statements - Ex: There are life forms in some planets. - Not 'He is tall' since we don’t know who is ‘he’ |
| Logical Operator: || | Takes the maximum value of A & B | Only 1 False - Ex: A ∨ B - Eng Words: And, but, also, more over |
| Logical Operator: && | Takes the minimum value of A & B | Only 1 True - Ex: A ^ B - Eng Words: And, but, also, more over |
| Logical Operator: Negation` | Opp. of A - Eng Words: It’s false that A |
| Logical Operator: Implication (→) | A → B | Only false when A is true & B is false - Eng Words: If A, then B | A implies B | A only if B |
| Logical Operator: Equivalence | ←→ | Only true when A & B are the same values - Eng Words: A if & only if B | A is necessary & sufficient for B |
| Order/ Precedence for Logical Connectives | 1. Innermost Parentheses 2. ` 3. ∨, ∧ 4. → 5. ←→ |
| Well-Formed Formulas (wff) | An expression that’s a legitimate string - PQRS: Letters to represent wff - Practice by Chapter 1.1 Exercise 1 (A - D) |
| Tautology vs Contradiction wff | Tautology: A wff that’s always true = 1 - Ex: A ∨ A` Contradiction: A wff that’s always false = 0 - Ex: A ∧ A` |
| Equivalent wff | P ←→ Q = (P → Q) ∧ (Q → P) - Ex: If P ←→ Q are both wff & a tautology, P can replace Q & vice versa |
| Determining T/F Combos for N Expressions | Use 2^N |
| Properties: Identity | - A v 0 = A - A ^ 1 = A |