As shown in the above figure, the grass is square with a side length of 12m, and there are trees (as shown in the figure) at the midpoint of two adjacent sides, and there are 6m sheep ropes. Then, on the grass, the range of sheep's activities is a circular range with a radius of 6m centered on the position of the tree (the midpoint of two adjacent sides). Specifically, in the grass, the activity range of two sheep is a semicircle with a radius of 6m with the midpoint of two adjacent sides as the center.

From any sheep's point of view, its overlapping position range is equivalent to a 90-degree sector with a radius of 6 meters minus the area of an isosceles right triangle with a waist length of 6 meters. The calculation is as follows:

The grassland area that both sheep can eat =(3. 14? x？ 6^2? x？ 90? /? 360? -? 1/2? x？ 6? x？ 6)? x？ 2? =? 20.52? (square meters)