Cutting in Half

Midpoints and bisectors

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Two equal circles around A and B give the perpendicular bisector of AB.
• It works because APBQ is a rhombus.
• The bisector is the set of points equidistant from A and B.

Steps

1. The perpendicular bisector
2. What the line means
3. Bisecting an angle
4. A circle through three points
5. Dig the well
6. Where the bisectors meet
7. Quarters