Central angles and arc measure
- Warm-up — 3 tasks
- Bridge — 3 tasks
- The measure of an arc — 3 tasks
- Adding arcs — 3 tasks
- Going Deeper — 6 tasks
- Practice — 27 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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Central Angles and Arc Measure: Which Number? Major, Minor and Reflex Angles — Cut & Glue Sort 25 minutes, including the cutting · 5 sheets
12 circles, each with one arc drawn heavy and one angle marked. Students do not compute: they sort each piece by what the heavy arc measures. The same as the marked angle, 360° minus it, or cannot tell, because the angle's vertex is not the center and it is not a central angle.
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Central Angles and Arc Measure: Which Arc? Minor and Major Arcs — Answer Maze 10–15 minutes · 4 sheets
8 boxes on one page, each a circle with its center marked, lettered points, and one or two central angles with their degrees. Students read the arc's name (two letters for the minor arc, three for a major arc or a semicircle) and find its measure in whole degrees. The wrong answers are the two commonest mistakes: reading the name the wrong way round, and using 360° where a diameter gives 180°. The row of box numbers at the foot is the check.
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Naming Arcs: Minor Arcs, Major Arcs and Semicircles — Mystery Picture 25–35 minutes · 5 sheets
25 circles, each with one arc drawn heavy and a name under it, such as arc ACB. Students compute nothing: two letters name the minor arc, three letters with a point of the arc in the middle name a major arc or a semicircle. Is the name right? Fill it or leave it white, and a picture appears.
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Central Angles and Arc Measure: Which Arc? Minor and Major Arcs — Scavenger Hunt a full class period · 13 sheets
16 cards around the room, each a circle with its center marked, lettered points, and one or two central angles with their degrees. Students read the arc's name (two letters for the minor arc, three for a major arc or a semicircle) and find its measure in whole degrees. Giving the angle that is drawn, using 360° where a diameter gives 180°, or going the wrong way round lands on a card that sends the group back, and a clean run is 8 lines on the record sheet.