The perpendicular bisector of a segment
- Three openings on one segment — 3 tasks
- What the opening has to be — 3 tasks
- Building it — 3 tasks
- The line that is perpendicular and still wrong — 3 tasks
- Going Deeper — 3 tasks
- Practice — 22 tasks
- Summary — 2 tasks
- Cool-down — 3 tasks
Classroom activities
Things a class does rather than writes on. Each one is a finished PDF: print it, cut it up if it says so, and hand it round.
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The Perpendicular Bisector: Cross, Touch or Never Meet? — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 segments, each with one arc struck from each end at the same opening and stopped short: predict whether the arcs will cross twice, touch once or never meet, check it by carrying them on with the compass, and glue each into its row — where touching once, at the middle, is the case that still gives no line.
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The Perpendicular Bisector: Do the Marks Prove the Line? — Mystery Picture 25–35 minutes · 4 sheets
25 strangers' finished attempts at the perpendicular bisector of a segment, every arc left on and no numbers: fill the square if the marks prove the line, leave it white if they show it wrong — unequal openings, a line through a single touching point, arcs on one side — or prove nothing at all.