底角的平分线是相等的。
弦的垂直平分线经过圆心，并且平分弦所对的两条弧。
A perpendicular bisector of a chord passes through the centre and bisects the arc.
一种角平分线绘制器，它由四条连杆铰接组成的菱形框架构成。
The utility model relates to an angle bisector drawing instrument which consists of a rhombus-shaped frame formed by articulating four connecting bars.
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