Homework Question

Hi Everyone,

I have a question about the homework that was due this morning at 6. For exercise 2.20 Grade Grinder kept giving me the feedback that my proof was correct but didn’t match the steps of the informal proof on page 52. When it says the proof should contain three steps matching the informal proof, I thought that would mean three steps after the Fitch line, so in addition to the three premises. Grade Grinder seems to be telling me that I shouldn’t have three non-premise steps. I’m wondering if the issue is actually about the rules I cited for each steps. Does anybody have an idea about which problem I was running up against? Thanks, Sara

1 thought on “Homework Question

  1. Elizabeth Sheedy

    Hi Sara,

    I ran into the same problem while working on 2.20; I kept trying to add too many inferences under the Fitch bar, or I was simply using the wrong rules and citations for the proof. I ended up keeping the original three premises as not to change the proof and then added whichever inferences were made in the informal proof as shown on page 52 to the area below the Fitch bar. (I ended up having three “steps” (maybe inferences is the better word) below the Fitch bar, including the conclusion seen in both the formal and informal proofs.) Since some of the rules (inverses, transitivity) aren’t specified on Fitch, Ana Con is a good friend. I hope this helps somehow, but please let me know if you would like me to clarify anything. Sincerely, Liz

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