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 minor, the other major.

The term *“spherical sector”* usually refers to the **salient sector**, or the sector that is convex. 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 *V* of a spherical sector that corresponds to a spherical cap of height *h* in a sphere of radius *r* is given by the relationship:

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

The total area *A* of a spherical sector of radius *R* and height *h* in a sphere of radius *r* is given by the formula:

\(A=2\pi rh+\pi Rr=\pi r\left ( 2h+R \right )\)