document.write( "Question 1003832: I can't figure out this exercise\r
\n" ); document.write( "\n" ); document.write( "B v R / (R v D)> J / ~J>~(B v A) // J\r
\n" ); document.write( "\n" ); document.write( "I have to use Indirect Proof but can only figure it out using Conditional. \n" ); document.write( "
Algebra.Com's Answer #620469 by Edwin McCravy(20055)\"\" \"About 
You can put this solution on YOUR website!
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document.write( "I only know the old way to do indirect proofs.  \r\n" );
document.write( "The modern way may be different, although the\r\n" );
document.write( "thinking process must be the same.  Maybe you can \r\n" );
document.write( "translate my old way into your new way, and maybe \r\n" );
document.write( "even teach me something about the modern way for\r\n" );
document.write( "indirect proofs in the thank-you note form below.  \r\n" );
document.write( "I would appreciate it.\r\n" );
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document.write( "Doing it the old way, we reach a contradiction\r\n" );
document.write( "t > f in statement 16.\r\n" );
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document.write( "Assume the premises are true, and the conclusion is false.\r\n" );
document.write( "So we have this:\r\n" );
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document.write( " 1. B v R is true\r\n" );
document.write( " 2. (R v D) > J is true\r\n" );
document.write( " 3. ~J > ~(B v A) is true\r\n" );
document.write( " 4. J is false\r\n" );
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document.write( " 5. ~f>~(B v A) is true           3,4, replacing J by f\r\n" );
document.write( " 6. t>~(B v A) is true            5, replacing ~f with t\r\n" );
document.write( " 7. ~(B v A) is true              6, the only way 6 can be true   \r\n" );
document.write( " 8. B v A is false                7, the negation is true\r\n" );
document.write( " 9. B is false; A is false        8, the only way B v A can be false \r\n" );
document.write( "10. f v R is true                 1,9, replacing B by f\r\n" );
document.write( "11. R is true                     10, the only way f v R can be true\r\n" );
document.write( "12. (f v D) > f  is true          2,4,11, replacing R and J by f\r\n" );
document.write( "13. f v D is false                13, the only way 12 can be true \r\n" );
document.write( "14. D is false                    13, the only way f v D can be false\r\n" );
document.write( "15. R v D is true                 11,14, R is true and D is false  \r\n" );
document.write( "16. t > f is true (contradiction) 2,15,4, replacing (R v D) by t, J by f \r\n" );
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document.write( "Edwin
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