Sector: An area inside the circle bounded by 2 radii and an arc.
A portion of the circle (area)
Arc: A curved segment of the circle.
A portion of the circle (perimeter)
Sector Area = (portion of circle)(area of entire circle)
Arc Length = (portion of circle)(circumference of entire circle)
Example: radius MOL =10 units central angle MOL = 80°
area of circle O = 100 π
circumference of circle O = 20 π
“portion of the circle”: 80°/360° = 2/9
therefore, sector area = 2/9 · 100 π = 69.8 sq. units (approximately)
arc length = 20 π = 13.96 units (approximately)