question archive Prove the following in SD+ #1

Prove the following in SD+ #1

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Prove the following in SD+

#1. 

1. R ⊃ (~A & T)

2. B ∨ ~S

3. R ∨ ~S  / A ⊃ B

#2. 

(A ⊃ A) ⊃ (~A & ~A) / A ∨ ~A

#3.

1. A ∨ B

2. C

3. (A & C) ⊃ D / D ∨ B

#4. 

[(A ∨ B) & (D & F)] ∨ [(A ∨ B) & C] / C ∨ F

#5 Show that the following pair of sentence is equivalent in SD+

 (A & B) ∨ [(C & D) ∨ A]

([(C ∨ A) & (C ∨ B)] & [(D ∨ A) & (D ∨ B)]) ∨ A

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#1

1. R ⊃ (~A & T)

2. B ∨ ~S

3. R ∨ ~S                                                          / A ⊃ B

4. ~R ∨ (~A & T)                                           1. Material Implication

5. ~R ? (A & T)                                             4. De Morgan's Theorem

6. (A & T)                                                     5. Simplification

7. A                                                                6. Simplification

8. B ? ~S                                                        2. De Morgan's Theorem

9. B                                                                 8. Simplification

10. A ⊃ B                                                      7, 9 Material Implication

 

#2

1. (A ⊃ A) ⊃ (~A & ~A)                                            / A ∨ ~A

2. ~ (A ⊃ A) ∨ (A & A)                                             1. Material Implication

3. ~ (A ⊃ A) ? (A & A)                                             2. De Morgan's Theorem

4. (A & A)                                                                  3. Simplification

5. A                                                                            4. Simplification

6. ~ (A ⊃ A)                                                              3. Simplification

7. ~ A ∨ ~A                                                               6. Material Implication

8. ~ A ? ~A                                                               7. De Morgan's Theorem

9. ~ A                                                                         8. Simplification

10. A ∨ ~A                                                                 5, 6 Disjunction

 

#3

1. A ∨ B

2. C

3. (A & C) ⊃ D                                                           / D ∨ B

4. ~ (A & C) ∨ D                                                       3. Material Implication

5. (~ A & ~ C) ? D                                                    4. De Morgan's Theorem

6. D                                                                             5. Simplification

7. A ? B                                                                     1. De Morgan's Theorem

8. B                                                                             7. Simplification

9. D ∨ B                                                                     6, 8 Disjunction

 

#4

1. [(A ∨ B) & (D & F)] ∨ [(A ∨ B) & C]                                            /C ∨ F

2. [(A ∨ B) & (D & F)] ? [(A ∨ B) & C]                                           1. De Morgan's Theorem

3. [(A ∨ B) & C]                                                                                2. Simplification

4. C                                                                                                    3. Simplification

5. [(A ∨ B) & (D & F)]                                                                      2. Simplification

6. (D & F)                                                                                         5. Simplification

7. F                                                                                                    6. Simplification

8. C ∨ F                                                                                              4, 7 Disjunction

 

#5

 (A & B) ∨ [(C & D) ∨ A]

1. (A & B) ∨ [(C & D) ∨ A]

2. (A & B) ? [(C & D) ∨ A]                                                  1. De Morgan's Theorem

3. [(C & D) ∨ A]                                                                    2. Simplification

4. [(C & D) ? A]                                                                   3. De Morgan's Theorem

5. (C & D)                                                                              4. Simplification

6. A                                                                                        4. Simplification

 

([(C ∨ A) & (C ∨ B)] & [(D ∨ A) & (D ∨ B)]) ∨ A

1. ([(C ∨ A) & (C ∨ B)] & [(D ∨ A) & (D ∨ B)]) ∨ A

2. [(C ∨ A) & (C ∨ B)]                                                                      1. Simplification

3. (C ∨ A)                                                                                           2. Simplification

4. C ? A                                                                                             3. De Morgan's Theorem

5. A                                                                                                     4. Simplification

 

 

-The above pair of sentences are logically equivalent because they entail each other.

Step-by-step explanation

-The following arguments are proved using SD to show that they are valid.

#1

1. R ⊃ (~A & T)

2. B ∨ ~S

3. R ∨ ~S                                                          / A ⊃ B

4. ~R ∨ (~A & T)                                           1. Material Implication

5. ~R ? (A & T)                                             4. De Morgan's Theorem

6. (A & T)                                                     5. Simplification

7. A                                                                6. Simplification

8. B ? ~S                                                        2. De Morgan's Theorem

9. B                                                                 8. Simplification

10. A ⊃ B                                                      7, 9 Material Implication

 

#2

1. (A ⊃ A) ⊃ (~A & ~A)                                            / A ∨ ~A

2. ~ (A ⊃ A) ∨ (A & A)                                             1. Material Implication

3. ~ (A ⊃ A) ? (A & A)                                             2. De Morgan's Theorem

4. (A & A)                                                                  3. Simplification

5. A                                                                            4. Simplification

6. ~ (A ⊃ A)                                                              3. Simplification

7. ~ A ∨ ~A                                                               6. Material Implication

8. ~ A ? ~A                                                               7. De Morgan's Theorem

9. ~ A                                                                         8. Simplification

10. A ∨ ~A                                                                 5, 6 Disjunction

 

#3

1. A ∨ B

2. C

3. (A & C) ⊃ D                                                           / D ∨ B

4. ~ (A & C) ∨ D                                                       3. Material Implication

5. (~ A & ~ C) ? D                                                    4. De Morgan's Theorem

6. D                                                                             5. Simplification

7. A ? B                                                                     1. De Morgan's Theorem

8. B                                                                             7. Simplification

9. D ∨ B                                                                     6, 8 Disjunction

 

#4

1. [(A ∨ B) & (D & F)] ∨ [(A ∨ B) & C]                                            /C ∨ F

2. [(A ∨ B) & (D & F)] ? [(A ∨ B) & C]                                           1. De Morgan's Theorem

3. [(A ∨ B) & C]                                                                                2. Simplification

4. C                                                                                                    3. Simplification

5. [(A ∨ B) & (D & F)]                                                                      2. Simplification

6. (D & F)                                                                                         5. Simplification

7. F                                                                                                    6. Simplification

8. C ∨ F                                                                                              4, 7 Disjunction

 

#5

 (A & B) ∨ [(C & D) ∨ A]

1. (A & B) ∨ [(C & D) ∨ A]

2. (A & B) ? [(C & D) ∨ A]                                                  1. De Morgan's Theorem

3. [(C & D) ∨ A]                                                                    2. Simplification

4. [(C & D) ? A]                                                                   3. De Morgan's Theorem

5. (C & D)                                                                              4. Simplification

6. A                                                                                        4. Simplification

 

([(C ∨ A) & (C ∨ B)] & [(D ∨ A) & (D ∨ B)]) ∨ A

1. ([(C ∨ A) & (C ∨ B)] & [(D ∨ A) & (D ∨ B)]) ∨ A

2. [(C ∨ A) & (C ∨ B)]                                                                      1. Simplification

3. (C ∨ A)                                                                                           2. Simplification

4. C ? A                                                                                             3. De Morgan's Theorem

5. A                                                                                                     4. Simplification

-Noticeably, the above pair of sentences are logically equivalent because they entail each other in the sense that the truth value of (A & B) ∨ [(C & D) ∨ A] /A is TRUE and the truth value of ([(C ∨ A) & (C ∨ B)] & [(D ∨ A) & (D ∨ B)]) ∨ A/A is also TRUE.

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