What is a sector?

• A. The portion of a circle bounded by two radii and one intercepted arc.
• B. The entire circle.
• C. A line segment along the circle.
• D. The distance from the center to the circle.

Answer: (A)

The concept being tested is what a sector is. A sector is the wedge-shaped part of a circle formed by two straight lines from the center to the circumference (the radii) and the curved edge between them (the intercepted arc). So the description that matches a sector is the region bounded by two radii and the arc between them. The entire circle is just the circle, not a sector. A line segment along the circle would be a chord or just part of the boundary, not the sector itself. The distance from the center to the circle is the radius, not a sector. Think of slicing a pie: the slice you get is a sector because it has two radii as its sides and the crust as the arc.