projective system of topological group

例句：

1. 1. Theprojective system is used to calculate thedistance between two points on a plane.
   投影系统用于计算平面上两点之间的距离。
2. 2. Inmathematics, the projective systemis used to study shapes and their properties.
   在数学中，投影系统用于研究形状及其属性。
3. 3. The projective system isa useful tool for visualizing complex geometricfigures.
   投影系统是一种有用的工具，用于可视化复杂的几何图形。