let X be Subset of MC-wff; :: thesis: for p, q being Element of MC-wff holds (p '&' q) => p in CnIPC X
let p, q be Element of MC-wff ; :: thesis: (p '&' q) => p in CnIPC X
for T being Subset of MC-wff st T is IPC_theory & X c= T holds
(p '&' q) => p in T ;
hence (p '&' q) => p in CnIPC X by Def15; :: thesis: verum