What is annular area?
Also know, what is meaning of annular region?
In mathematics, an annulus (the Latin word for "little ring" is anulus / annulus, with plural anuli / annuli) is a ring-shaped object, a region bounded by two concentric circles. The adjectival form is annular (as in annular eclipse).
In this manner, what is annular domain?
Annular domain. From Encyclopedia of Mathematics. A doubly-connected planar domain between two closed Jordan curves without common points, one of each encloses the other. For an annular domain with respect to a quadratic differential, see Global structure of trajectories of a quadratic differential.
The circumference = π x the diameter of the circle (Pi multiplied by the diameter of the circle). Simply divide the circumference by π and you will have the length of the diameter. The diameter is just the radius times two, so divide the diameter by two and you will have the radius of the circle!