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 \left( \prod_{n = 1}^N x_n \right) = \sum_{n = 1}^N \log_a x_n \end{equation}