directrix of a linear congruence

例句：

1. 1.The architect drew a directrix on the sketch.
   建筑师在草图上画了一条直线。
2. 2.The engineer used a directrix to measure the angle between two points.
   工程师使用一条直线来测量两点之间的夹角。
3. 3.The carpenter cut a directrix to fit the door frame.
   木匠切割了一段直线来适配门框。