The proof of this is similar to that of Lemma X above and Lemma X below. \end{iexample} Example: Given vector spaces , and , a bilinear map $ f{\colon}\linebreak[0] U \times V \to W $ is a function that is linear in each variable: $ f(u, v_1 + \lambda v_2) &= f(u, v_1) + \lambda f(u, v_2), \ f(u_1 + \lambda u_2, v) &= f(u_1, v) + \lambda f(u_2, v) $ for all , , and scalars . A good example is the scalar product (dot product), which is a bilinear map of real vector spaces.