Website and domain for sale:

How to solve the problem, what is the distance between the posts?

The middle of the cable is hanging at a height of 5 meters. Cable length of 30 meters, and its length is half of 15 meters. In addition, the distance from the middle of the cable up to the tops of the pillars, too, is 15 meters. This is possible only when both halves of the cable hanging vertically from the tops of the pillars. That is, the distance between the pillars is zero meters.
Answer add