Editing Unit interval (section)

===Orientation===
The unit interval is a [[curve]]. The open interval (0,1) is a subset of the [[positive real numbers]] and inherits an orientation from them. The [[curve orientation|orientation]] is reversed when the interval is entered from 1, such as in the integral <math>\int_1^x \frac{dt}{t} </math> used to define [[natural logarithm]] for ''x'' in the interval, thus yielding negative values for logarithm of such ''x''. In fact, this integral is evaluated as a [[signed area]] yielding ''negative area'' over the unit interval due to reversed orientation there.