Hi: I am going over Lee's Riemm. mflds, and there is an exercise that asks: Let M<M' (< is subset) be an embedded submanifold. Show that any vector field X on M can be extended to a vector field on M'. Now, I don't know if he means that X can be extended to the _whole_ of M', because otherwise, there is a counterexample: dt/t on (0,1) as a subset of IR cannot be extended to the whole of IR. Anyone know?. What Would Gauss Do?