Proofs II, #11

 

derive ~S

 

1. (F & ~G) v (T & ~W) premise  
2. (W & H) premise  
3. ~(F G)  (H ~S) premise  
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Strategy

Get ~(F G)

which is ~(~F v G)

which is (F & ~G)

so get (F & ~G) by getting

~(T & ~W)

which is (~T v ~~W) or (~T v W)

But we have (W & H) and so we have W and so ~T v W by disjoining.