Circular or elliptical disk segment region consumed by Area/Perimeter/RegionCentroid
与 .wl 参考的差异： `DiskSegment` and other region primitives are not drawn
DiskSegment[{x, y}, r, {θ 1, θ 2}]
DiskSegment[{x, y}, {r x, r y}, {θ 1, θ 2}]
Area[DiskSegment[{0, 0}, 1, {0, Pi}]]
→ Pi/2Graphics[DiskSegment[{0, 0}, 1, {0, Pi}]]
→ -Graphics-Graphics[{Orange, DiskSegment[{0, 0}, 1, {0, 3Pi / 4}]}]
→ -Graphics-