let F1, F2, F3, G be MC-formula; :: thesis: ( {F1,F2,F3} |-_IPC G implies {F2,F3} |-_IPC F1 => G )
{F1,F2,F3} = {F2,F3} \/ {F1} by ENUMSET1:2;
hence ( {F1,F2,F3} |-_IPC G implies {F2,F3} |-_IPC F1 => G ) by Th53; :: thesis: verum