let p, q be Element of CQC-WFF ; :: thesis: for x being bound_QC-variable holds (Ex x,(p => q)) <=> ((All x,p) => (Ex x,q)) is valid
let x be bound_QC-variable; :: thesis: (Ex x,(p => q)) <=> ((All x,p) => (Ex x,q)) is valid
( (Ex x,(p => q)) => ((All x,p) => (Ex x,q)) is valid & ((All x,p) => (Ex x,q)) => (Ex x,(p => q)) is valid ) by Th65;
hence (Ex x,(p => q)) <=> ((All x,p) => (Ex x,q)) is valid by Lm14; :: thesis: verum