2. These are essentially what Nos 26 (skip line 1 and make lines 2,3 the premises) and 27 amount to, from Ex 3.3.1. (Change A,B,C to p,q,r)
3. Exercise 4.3.1 #7. There is one solution in the text; HERE is another
4. The derivation for the first one also comes from Ex 3.3.1, #29, although the tableaux are simpler (for both). Here they are. And here is the missing derivation.
5. This one is the Trekkie example from the text - the derivation is in Chp 3, and the tableau in Chp 4.
