Whatever the subjective concept of beauty may be, it still has some common to all criteria.

One of these criteria - symmetry, because very few people like the person in the eye which are located on different levels.

Symmetry is always assumes a rotary axis, also referred to as the symmetry axis.

In a broad sense, the symmetry referred to the preservation of something unchanged under some transformation. Enjoy this property and some geometric shapes.

## Geometric symmetry

With reference to FIG geometric symmetry means that if convert this figure - for example, turn - some of its properties remain unchanged.

The possibility of such changes differs fromfigure to figure. For example, the range can be as much as necessary to rotate around a point located in its center, it will remain a circle, there is nothing for it will not change.

The concept of symmetry can be explained without resorting torotation. Suffice it to navigate through the center of the circle line and build anywhere in the figure perpendicular to the segment joining two points on a circle. The point of intersection with the line shall divide this segment into two parts, which will be equal to each other.

In other words, a straight figure divided into twoequal parts. Parts of the figure point located on the lines perpendicular to this, are equidistant from it. Here is the direct and will be called the axis of symmetry. The symmetry of this kind - a relatively straight - called axial symmetry.

## The number of axes of symmetry

Different figures the number of axes of symmetry willdifferent. For example, the circle and the sphere of the set of axes. In an equilateral triangle is the axis of symmetry is perpendicular dropped on each of the parties, therefore, has three axes. The square and rectangle can hold four axes of symmetry. Two of them are perpendicular to the sides of the rectangle, while the other two are the diagonals. And here at the axis of symmetry of an isosceles triangle, only one, located by the parties in equal honey.

The axial symmetry found in nature. It can be seen in two ways.

The first type - radial symmetry, assumingmultiple axes. It is typical, for example, sea stars. A more highly developed organisms characterized by bilateral or bilateral symmetry with a single axis, which divides the body into two parts.

The human body is also characterized by bilateralsymmetry, but it can not be called perfect. Symmetrically arranged legs, arms, eyes, lungs, but not the heart, liver or spleen. Deviations from the bilateral symmetry visible even externally. For example, rarely happens to a man on both cheeks have the same birthmarks.