$f \in \Re_{[a,b]}$ $\Leftrightarrow$ $\forall \epsilon > 0 \exists P \underline S(P) — \overline s(P) < \epsilon$ $\Leftrightarrow$ $\underline I = \overline I$
$f \in \Re_{[a,b]}$ $\Leftrightarrow$ $\forall \epsilon > 0 \exists P \underline S(P) — \overline s(P) < \epsilon$ $\Leftrightarrow$ $\underline I = \overline I$
Это я