fof(ax_D3a,axiom,(![A,B,C,D,P]:((point(A)&point(B)&point(C)&ncol(A,B,C)&point(D)&plane(P)&inc_po_pl(A,P)&inc_po_pl(B,P)&inc_po_pl(C,P)&ninc_po_pl(D,P))=>(ncop(A,B,C,D))))).
