It is shown that using Bernstein polynoms can one prove the classical Lebesgue and Baire theorems on separately continuous functions. It is obtained that a compact $Y$ is metrizable iff identical mapping $I: C_p(Y) → C_u(Y)$  belongs to the first Baire class $B_1(C_p(Y), C_u(Y))$ or for every topological spaces $X$ the inclusion $C(X, C_p(Y)) ⊆ B_1(X, C_u(Y))$ holds.

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