However subjective the concept of beauty may be, it still has some criteria common to all.
One of these criteria is symmetry, because few people like the face, on which the eyes are located at different levels.
Symmetry always assumes the presence of a rotational axis, also called the axis of symmetry.
In a broad sense, symmetry refers to the preservation of something unchanged with some kind of transformation. Some geometric figures also possess this property.
With respect to a geometric figure, symmetry means that if a given figure is transformed - for example, rotate - some of its properties will remain the same.
The possibility of such transformations differs fromFigures to the figure. For example, a circle can be rotated around a point located in its center, it will remain around, nothing for it will change.
The concept of symmetry can be explained without resorting toRotation. It is sufficient to draw a straight line through the center of the circle and construct a line perpendicular to it that connects two points on the circle in any place of the figure. The point of intersection with the straight line will divide this segment into two parts, which will be equal to each other.
In other words, the straight divided the figure into twoEqual parts. The points of the parts of the figure located on the straight lines perpendicular to this are at an equal distance from it. This one is straight and will be called the axis of symmetry. Symmetry of this kind - relatively straightforward - is called axial symmetry.
Number of axes of symmetry
For different figures, the number of axes of symmetry will beDifferent. For example, a circle and a ball have such axes. In an equilateral triangle, the axis of symmetry is the perpendicular, which is lowered to each side, hence it has three axes. Four squares of symmetry can be drawn by a square and a rectangle. Two of them are perpendicular to the sides of the quadrangles, and the other two are diagonals. But in an isosceles triangle, the axis of symmetry is only one, which is located equal to its sides.
Axial symmetry is also found in nature. It can be observed in two versions.
The first type is the radial symmetry, assumingPresence of several axes. It is typical, for example, for sea stars. More highly developed organisms have a bilateral, or two-sided symmetry with a single axis dividing the body into two parts.
The human body also has a bilateralSymmetry, but it can not be called ideal. Symmetrically located legs, hands, eyes, lungs, but not the heart, liver or spleen. Deviations from bilateral symmetry are noticeable even externally. For example, it is extremely rare for a person on both cheeks to have the same birthmark.