I am working on a tautology question and understand most of the answer except for one part. I need to show that the following is a tautology:

<=> means equivalent

Code: Select all

```
p -> [(~p) -> q)]
<=> ~p v [~(~p v q)] <- this line - why the first ~? How do I get it? Is it because of the already existing ~p?
<=> ~p v [ p v q]
<=> (~p v p) v q
<=> T v q
<=> t
```

Thanks for any help,

Tony