concurrent lines的用法和样例：
例句
- Construct an animation displaying a nephroid sliding along three fixed concurrent lines meeting at 120 degrees.
建构一动态绘图。展示肾脏线的滚动，沿著共点及间隔120度的三条直线。 - This paper discusses the relations between concurrent lines theorem and collinear points theorem of the projection geometry, and obtains their duality relation and equivalence relation.
对射影几何中的共点线（共线点）定理之间的关系进行探讨，给出它们有关的对偶关系和等价关系。
