let A be QC-alphabet ; :: thesis: for p, q being Element of QC-WFF A holds Fixed (p => q) = (Fixed p) \/ (Fixed q)
let p, q be Element of QC-WFF A; :: thesis: Fixed (p => q) = (Fixed p) \/ (Fixed q)
p => q = 'not' (p '&' ('not' q)) by QC_LANG2:def 2;
hence Fixed (p => q) = Fixed (p '&' ('not' q)) by Th39
.= (Fixed p) \/ (Fixed ('not' q)) by Th42
.= (Fixed p) \/ (Fixed q) by Th39 ;
:: thesis: verum