# Centre (geometry)

- The term focus is used in geometry in the following contexts: At a distance, a circle, a sphere, or in general for an N -dimensional sphere, the center is the point which has the same ( minimum ) distance of all points of this sphere. This definition can generally make in (complete) metric spaces.
- In conics and quadrics in the described by second order surfaces (eg ellipsoids or cones), the centers of which are the fixed elements of a mirror, which transfers the predetermined figure in itself. All conic sections with the exception of the parabolas have exactly one center; a second order surface can not just have one or a whole line or level of midpoints. Did she just a center, it is called Mittelpunktsquadrik.
- Colloquially, the term center is also used frequently in the sense of gravity.
- See also: Excellent points in the triangle, middle dot, optical center

- Geographic centers: List of geographical centers.

## Description by Coordinates

### Route

If the end point and the starting point of a route is known, one can also determine the coordinates of the center on the relationships, or at a distance in space with.

### Circle / Sphere

Is a circle equation of the form given, so you can specify on the coordinates of the center directly. In the equation of a sphere about the Z -axis is expanded. The center is thus.