Bisecting an angle
- The fold that halves an angle — 3 tasks
- From the fold to a plan — 3 tasks
- Bisecting with three arcs — 3 tasks
- Which ray can you trust? — 3 tasks
- Going Deeper — 6 tasks
- Practice — 24 tasks
- Summary — 2 tasks
- Construct one and check it — 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.
-
Bisecting an Angle: The Named Angle, a Side, or Another Angle? — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 triangles, each with an instruction to bisect a named angle and somebody's finished compass marks, stopped before the line: sort each by what the marks are built for — the named angle, the perpendicular bisector of a side, or the bisector of a different angle, the one error no fold catches.
-
Bisecting an Angle: Do the Marks Prove the Ray? — Mystery Picture 25–35 minutes · 4 sheets
25 strangers' finished attempts to bisect an angle, every arc left on and no numbers: fill the square if the marks prove the ray, leave it white if they do not — a reset compass, a protractor, arcs struck from the vertex, arcs that never meet, or a ray that misses the corner.