Complementary Subspaces

Let $$V$$ and $$W$$ be subspaces of $$U$$, i.e., $$V,W \subseteq U$$. $$V$$ and $$W$$ are called complementary subspaces if V$$ and $$w \in W$$, and
 * 1) Any $$u \in U$$ can be expressed as $$u=v+w$$ for some $$v \in
 * 1) The intersection of $$V \text{ and } W$$ contains only 0 (which is the requirement to be a subspace), i.e. $$V \cap W = \{0\}$$