相交线 meaning in English

intersecting lines
intersection line

In addition , if your line of sight is perpendicular to the line of intersection between the mirrors , then no matter where you are , your image will always be visible as long as you can see the line of intersection ( note that the angle between the orthogonal mirrors must be accurate )
直角镜有一个有趣的特性，就是当你将直角镜转动时，镜像的转动角度会大一倍。此外，只要直角镜面相交线与视线垂直，无论你站在甚么地方，只要看到相交线，就可以看到自己的影像(要注意镜子的夹角必须准确) 。
In addition , if your line of sight is perpendicular to the line of intersection between the mirrors , then no matter where you are , your image will always be visible as long as you can see the line of intersection note that the angle between the orthogonal mirrors must be accurate
直角镜有一个有趣的特性，就是当你将直角镜转动时，镜像的转动角度会大一倍。此外，只要直角镜面相交线与视线垂直，无论你站在甚么地方，只要看到相交线，就可以看到自己的影像要注意镜子的夹角必须准确。