1.4.2—Arc length and sector area

For radius r and angle θ in radians, arc length s=rθ and sector area A=½r²θ. Segment area requires subtracting the corresponding triangle from the sector.

Use the same angle units in every term, identify whether the question asks for sector or segment, and check that 0≤θ≤2π for an ordinary sector.

With r=4 and θ=π/3, s=4π/3 and sector area=8π/3. A minor segment would be this sector minus ½r²sinθ.

Sector area is not ½r²sinθ; that is the triangle area used when a segment is formed.