Lecture #12 continued our look at propositional logic. In particular it looked at various proof mechanisms.
Notes are available in two formats:
The only way you will get good at doing proofs (and they are the kind of thing which have a habit of cropping up in exams) is by working through ones done by other people and doing them yourselves.
So, you should go through the examples in the notes carefully (and then look at the homework examples).