According to abbreviationfinder.org, corona is a concept with multiple uses. The ornament made with flowers and other materials that is placed on the head and represents something symbolic; a round object, especially if it is on a high place; the grouping of leaves and flowers arranged in a circular manner; the currency of certain nations; the dental region that appears on the gum, and the artificial object that cares for or replaces this dental part are called the crown.

From the Latin *circularis*, circular is something linked to a circle. The concept is also used to name the procedure that seems to never end, since it ends in the same place where it begins, and the instruction of an authority addressed to his subordinates.

The notion of circular crown is used in the field of geometry to refer to the plane figure that is determined by a pair of concentric circles. If you want to mentally graph, you need to imagine a circle inside a larger one; then, we visually subtract the space occupied by the smaller one, obtaining a circular strip with a “hollow” center, and that is precisely the circular crown of the two figures.

To understand this definition, we must first be clear about the notion of circumference: it is a closed, curved and flat line, with points equidistant from the fixed and coplanar point called the center ; the distance between any of the points and the center is known as the radius and the segment formed by two aligned radii, on the other hand, is called the diameter.

The area of a circular crown is obtained by previously calculating the surface of each of the circles; To do this, we will first determine the radius r, belonging to the small figure, and R, of the large one. Having identified both areas, we subtract the square of the smaller multiplied by pi, from the square of the larger multiplied by pi: pi x R x R – pi x r x r, which is equivalent to pi x (R x R – r x r), if we remove the common factor.

A concept associated with the circular crown is that of the circular trapezoid, which is nothing more than a trapezoid whose bases have a curvature. Again, it is very useful to try to mentally graph the term to fully internalize and understand it; Thinking of a circular crown, if we “cut” a portion, as if it were a cake, we would obtain a figure similar to a rectangle, but crooked. To find its area, it will also be necessary to calculate the surfaces of the concentric circles in question, with which we will find the area of the circular crown.

Once we have that value, it is necessary to understand that it is the surface of a 360 degree circular crown, that is, it represents the area of the closed figure. However, since in this case we are interested in finding out the surface of a portion of said crown, the angle will be clearly smaller. With this data in hand, which for the example we can represent with 56 degrees, the last part of this calculation is very simple, since it is a simple rule of three: if 360 degrees corresponds to the area a, for 56 degrees its area will be 56 xa / 360, which will give us a result in the unit of measure we have chosen, which may well be centimeters, always squared.

The circular crown is a relatively difficult geometric figure to represent graphically, but extremely common in everyday life, since it is found in countless logos and symbols, such as the signs used to prohibit vehicle parking in certain areas or the signs that indicate the maximum speed of a highway.