Sector (symbol:? ) is a part of a circle surrounded by two radii and an arc. It is called a small sector in a smaller area and a large sector in a larger area. In the picture on the right, θ is the angular radian of the sector, R is the radius of the circle, and L is the arc length of the small sector.
Extended data
Formula related to circle:
1, circular area: S=πr? ，S=π(d/2)？ . (d is the diameter and r is the radius).
2. area of semicircle: s semicircle = (π r 2)/2. (r is the radius).
3. Ring area: s great circle -S small circle = π (r 2-r 2) (r is the radius of great circle and r is the radius of small circle).
4. Circumference: C=2πr or c = π d..(d is the diameter and r is the radius).
5. The circumference of a semicircle: d+(πd)/2 or d+π r (d is the diameter and r is the radius).
6. The area of the circle where the sector is located is divided by 360 and multiplied by the angle n of the central angle of the sector, as shown below:
S=n/360×πr？
S=πr？ ×L/2πr=Lr/2(L is arc length and r is sector radius)