Sector

Properties

• Angular sector
  In a plane, a geometric figure defined by the union or the intersection of two half-planes whose boundaries intersect at a point O called the vertex of the angular sector.
  
• Circular sector
  The portion of a circle between two radii.
  
  The area of a circular sector that corresponds to an angle of \(α\)° in a circle of radius \(r\) has the relationship :
  \(A=\dfrac {α} {360}\pi r^{2}\)

• Spherical sector
  If the radius of a sphere revolves around the boundary of a small circle of the sphere, it forms a conical surface and divides the sphere into two spherical sectors, one salient, the other re-entrant. The term “spherical sector” usually refers to the salient sector.
  This sector can be described as the union of a spherical cap and a cone whose vertex is at the centre of the sphere and whose base corresponds to the base of the spherical cap.
  
  The volume of a spherical sector that corresponds to a spherical cap of height \(h\) in a sphere of radius \(r\) has the relationship :
  \(V=\dfrac {2 \pi r^{2} h} {3}\)