Definition:Natural Logarithm/Positive Real/Definition 1

Definition
Let $x \in \R$ be a real number such that $x > 0$.

The (natural) logarithm of $x$ is defined as:


 * $\displaystyle \ln x := \int_1^x \frac {\d t} t$

Also see

 * Equivalence of Definitions of Real Natural Logarithm