reserve V,X,Y for RealLinearSpace;
reserve u,u1,u2,v,v1,v2 for VECTOR of V;
reserve a for Real;
reserve V1,V2,V3 for Subset of V;
reserve x for object;
reserve W,W1,W2 for Subspace of V;
reserve w,w1,w2 for VECTOR of W;

theorem Th9:
  x in W implies x in V
proof
  assume x in W;
  then
A1: x in the carrier of W;
  the carrier of W c= the carrier of V by Def2;
  hence thesis by A1;
end;
