Author note — to cover

Arc length as the angle over 360 of the circumference, plus two radii for a sector's perimeter, exact and rounded, major arcs via the reflex angle. G18 makes arcs and sectors both tiers, not Higher. Reversed problems recovering the angle sit on Finding the angle of a sector. (G18)

• Fluency — direct questions on arc length, limited to this lesson's stated scope (4 questions).
• Application — use the same skill in unfamiliar or contextual questions without introducing a later method (4 questions).
• Check — questions built around the exclusions and likely misconceptions named in the lesson brief (4 questions).