mid-point of class

例句：

1. 1. The mid-point of the lineis exactly at the intersection of the twolines.
   这条线的中点正好是两条线相交的地方。
2. 2. The mid-point ofthe circle is the center of the circle.
   圆的中点是圆的中心。
3. 3. Themid-point of the triangle divides each side into two equal parts.
   三角形的中点将每条边分成两个相等的部分。