Y by
A square region of side
contains a water source that supplies an irrigation system constituted by several straight channels forming polygonal lines. Considers the source as a point and each channel as a line segment.
Knowing that a point is irrigated if it is not more than
distance from any channel and that the system was designed so that the entire region is irrigated, proves that the total length of irrigation channels exceeds
.

Knowing that a point is irrigated if it is not more than

