理解角（12岁以上）
Understanding angles (age 12+)
用直尺和圆规完成基本尺规作图：作线段的垂直平分线、过直线上或直线外一点作该直线的垂线，以及作一个角的平分线。
Use ruler and compasses to perform standard constructions: perpendicular bisector of a line segment, perpendicular to a line from or at a given point, and bisecting an angle
学习证据 / Evidence
- 用圆规和直尺作一条线段的垂直平分线
- 作一个角的平分线，并通过测量两个半角来验证
- 仅用圆规从一点向一条直线作垂线
- Construct the perpendicular bisector of a line segment using compasses and a straight edge
- Construct an angle bisector and verify by measuring both halves
- Construct a perpendicular from a point to a line using compasses only
评估问题 / Assessment
如果{{name}}只有一把直尺和一副圆规，能否不用量角器，画出一条直线，使它恰好把另一条线段垂直平分？
If {{name}} has only a ruler and a pair of compasses, can they construct a line that cuts another line segment exactly in half at a right angle — without using a protractor?