concurrent lines的用法和樣例：
例句
- Construct an animation displaying a nephroid sliding along three fixed concurrent lines meeting at 120 degrees.
建構一動態繪圖。展示腎臟線的滾動，沿著共點及間隔120度的三條直線。 - 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.
對射影幾何中的共點線（共線點）定理之間的關係進行探討，給出它們有關的對偶關係和等價關係。
