Friday, September 27, 2013
(LCR) Protocol for formal proofs
Many of you lost points on today's quiz, not because you couldn't solve the problems but because you were sloppy about protocol. I'm going to be an absolute control freak about this, for when proofs start to get complicated any deviation from procedure can lead to mistakes in the proof. So NUMBER ALL STEPS IN A PROOF, and JUSTIFY EVERY LINE. If a proposition is a premise, you must write "Prem." after it. Following the last premise (properly so labeled), put a forward slash, three dots indicating "Therefore," and the conclusion which you are attempting to demonstrate. Each subsequent step requires a justification (the numbers of relevant previous steps and the rule(s) of inference you are using to justify the step).
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I did have a question that I forgot to voice at the beginning of the quiz, professor. It didn't occur to me until we had finished, but would you prefer that we use the 'QED' abbreviation next to the final line of a proof to show that it is the end of the problem? If so, will we be marked down for not using it?
It's always a good idea to tack that on at the end, indicating that you believe you have established the validity of the argument with the formal proof. I'm not going to subtract points for not doing so, but when we use a procedure over and over in class, my expectation is that students will notice and imitate it.
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