Question

3.Give formal proof to show that the following argument forms are valid.
a.  ⟹ , ├ .
b. ⟹ , , ⟹ ├ .
c. ⟹ ,  ⟹  ├  ⟹ .

Answer 1

Answer:

Valid: an argument is valid if and only if it is necessary that if all of the premises are true, then the conclusion is true; if all the premises are true, then the conclusion must be true; it is impossible that all the premises are true and the conclusion is false. Invalid: an argument that is not valid.

Answer 2

Answer:

Valid: an argument is valid if and only if it is necessary that if all of the premises are true, then the conclusion is true; if all the premises are true, then the conclusion must be true; it is impossible that all the premises are true and the conclusion is false. Invalid: an argument that is not valid.