reserve r,s,t,u for Real;
reserve V for RealLinearSpace,
  v,w for Point of V;

theorem :: GOBOARD7:7
  1/2*(v+w) in LSeg(v,w)
proof
  1/2*(v+w) = (1-1/2)*v+1/2*w by RLVECT_1:def 5;
  hence thesis;
end;
