reserve AS for AffinSpace;
reserve a,b,c,d,a9,b9,c9,d9,p,q,r,x,y for Element of AS;
reserve A,C,K,M,N,P,Q,X,Y,Z for Subset of AS;

theorem
  M is being_line & X is being_plane & M c= X implies M '||' X
proof
  assume that
A1: M is being_line and
A2: X is being_plane & M c= X;
  M // M by A1,AFF_1:41;
  hence thesis by A1,A2,Th41;
end;
