A portion of space.

In geometry, the term “sector” refers to a portion of two-dimensional or three-dimensional space.

In geometry, the term “sector” refers to a portion of two-dimensional or three-dimensional space.

### 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 :

\(V=\dfrac {2 \pi r^{2} h} {3}\)