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I have to prove this in Fitch without using any of the cons

closed as off-topic by Conifold, Eliran, Graham Kemp, YiFan, Mauro ALLEGRANZA Mar 21 at 7:03

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question is missing context. Please improve the question by providing additional context, which ideally includes your thoughts on the problem and any attempts you have made to solve it. This information helps others identify where you have difficulties and helps them write answers appropriate to your experience level." – Conifold, Eliran, Graham Kemp, YiFan, Mauro ALLEGRANZA
If this question can be reworded to fit the rules in the help center, please edit the question.

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    We do not do HW for people. Present your own attempt and we can help correct mistakes, if any. – Conifold Mar 20 at 21:09
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    There is a good reason you are having trouble. (A ∨ D) is not logically entailed by (A V B) and (¬C ∨ ¬B). Is there something missing or miscopied? – Graham Kemp Mar 20 at 23:13
  • I think the question is not off-topic, but I'm not saying I understand it. Where does the statement D come from? Is it random? "A or D" is true in the sense that once you say A is true, then "A or [anything]" is true. – Mark Andrews Mar 21 at 17:57
  • @MarkAndrews That is why the question is off topic. It is missing the details needed to answer it. – Graham Kemp Mar 21 at 22:03
  • @GrahamKemp In general, I think logic questions are on topic. If the question is missing pieces to the puzzle, I see that as a different problem. – Mark Andrews Mar 21 at 23:00
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Below is a generated truth table for the statement "((A or B)&&(~C or ~B))=>(A or D)".

Note the line where the result is False (F).

enter image description here


Stanford Truth Table Tool, http://web.stanford.edu/class/cs103/tools/truth-table-tool/

  • Is the implication the primary connective in this truth table? The implication seems to be the main connective in what is written and --NOT the disjunction. The way you wrote this it appears you are focusing on the disjunction. The row looks correct on if the implication was used just weird the way you aligned the table. – Logikal Mar 24 at 19:14
  • Yes, it is the implication that is the main connective: the conjunction of the two premises imply the disjunction "A v D". The table is a screenshot of the output of the truth table tool. I did nothing more than enter the formula into the tool. – Frank Hubeny Mar 24 at 19:18

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