In the proof you assumed the negation of (B & C). My question is, why can't we use disjunctive syllogism on lines 1 & 4 to get B & C for line 5 instead of assuming the negation? Then we can simplify line #5 B & C to get line #6 B and line #7 C. Then we can use addition (or) on line #6 to get line #8 (A or B ) . Then modus ponens on line #3, #8 to get line #9 (D or E). Then use disjuntive syllogism on line #2, #9 to get line #10 D. Then using conjunction from line#7 ,#10 to get line #11 C & D? is my reasoning correct or no? thanks!
37:22 NO! Please explain more! I am confused on why you were able to prove ~P v Q in the subproofs. You mentioned you could not do this in the video that has problem #14 ( ua-cam.com/video/y3Q4Ybp6mdI/v-deo.html )
@0:08 Proof #24 ** @12:20 Proof #25 ** @17:42 Proof #26 ** @20:25 Proof #27 ** @29:27 Proof #28 ** @44:09 Proof #29
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(20:17)...yes, you are the best! 😁Thanks for your knowledge and hard work.👍
Thank you very much William, you saved my sleepless night !!
20:18 You are goddamn right
Great video about natural deduction! Cool shirt dude
In the proof you assumed the negation of (B & C). My question is, why can't we use disjunctive syllogism on lines 1 & 4 to get B & C for line 5 instead of assuming the negation? Then we can simplify line #5 B & C to get line #6 B and line #7 C. Then we can use addition (or) on line #6 to get line #8 (A or B ) . Then modus ponens on line #3, #8 to get line #9 (D or E). Then use disjuntive syllogism on line #2, #9 to get line #10 D. Then using conjunction from line#7 ,#10 to get line #11 C & D? is my reasoning correct or no? thanks!
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07:10 probably a stupid question, but couldn't you just get a contradiction by conjunction introduction with 1 and 14 directly?
37:22 NO! Please explain more! I am confused on why you were able to prove ~P v Q in the subproofs. You mentioned you could not do this in the video that has problem #14 ( ua-cam.com/video/y3Q4Ybp6mdI/v-deo.html )