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+2 votes

Choose the correct alternatives (More than one may be correct).

Indicate which of the following well-formed formulae are valid:

  1. $\left(P\Rightarrow Q\right) {\wedge} \left(Q \Rightarrow R\right) \Rightarrow \left(P \Rightarrow R\right)$
  2. $\left(P\Rightarrow Q\right) \Rightarrow \left( \neg P \Rightarrow \neg Q\right)$
  3. $\left(P{\wedge} \left(\neg P \vee  \neg Q\right)\right) \Rightarrow Q$
  4. $\left(P \Rightarrow R\right) \vee \left(Q \Rightarrow R\right) \Rightarrow \left(\left(P \vee Q \right)  \Rightarrow R\right)$
asked in Mathematical Logic by Veteran (29.5k points)   | 147 views

A is true it is Hypothetical syllogism.


In classical logic, hypothetical syllogism is a valid argument form which is a syllogism having a conditional statement for one or both of its premises. If I do not wake up, then I cannot go to work. If I cannot go to work, then I will not get paid. Therefore, if I do not wake up, then I will not get paid.



[(P⇒Q)∧(Q⇒R)]      =====>      (P⇒R)

----------------------                        -----------

      T                                         F

You Can Not find   T====>F

So this formula is always true

1 Answer

+1 vote
Create a logic table for each of the given formula and check if we are getting true everywhere.
answered by Veteran (15k points)  

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