reserve V for RealLinearSpace;
reserve u,u1,u2,v,v1,v2,w,w1,y for VECTOR of V;
reserve a,a1,a2,b,b1,b2,c1,c2 for Real;
reserve x,z for set;

theorem Th11:
  u,u#v // u#v,v
proof
  set p = u#v;
  2*(p-u) = v-u by Th10
    .= 2*(v-p) by Th10;
  hence thesis by ANALOAF:def 1;
end;
