let x be bound_QC-variable; :: thesis: for p being Element of QC-WFF holds Fixed (Ex x,p) = Fixed p
let p be Element of QC-WFF ; :: thesis: Fixed (Ex x,p) = Fixed p
Ex x,p = 'not' (All x,('not' p)) by QC_LANG2:def 5;
hence Fixed (Ex x,p) = Fixed (All x,('not' p)) by Th50
.= Fixed ('not' p) by Th55
.= Fixed p by Th50 ;
:: thesis: verum