Let $\log_a$ be the D866: Standard real logarithm function in base $a \in (0, \infty) \setminus \{ 1 \}$.
Let $x_1, \ldots, x_N \in (0, \infty)$ each be a D5407: Positive real number.

Then \begin{equation} \log_a(x_1 x_2 \cdots x_N) = \log_a(x_1) + \log_a(x_2) + \cdots + \log_a(x_N) \end{equation}