How can we measure convoluted lines with a straight ruler?
We apply, again and again, the ruler along the curve. If the length of the ruler is negligible compared to the curvature or the irregularities of the line, we can approach the real length. This length is the number of unit segments used multiplied by the length of the segment, when this length tends towards 0. In other words, if we divide by 2 the length of the unit, we multiply by 2 the number of segments used to measure the line, but this is true only when the segment length tends towards 0.
