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

Geometric symmetry

With regard to the geometry symmetry means that if the figure of the convert – for example, to turn some of its properties will remain the same.

The possibility of such transformation varies from figure to figure. For example, round one may rotate around a point located in its center, he will remain around, nothing for him will not change.

The concept of symmetry can be explained without recourse to rotation. Enough to push through the center of the circle and the straight to build in any place of the figure perpendicular a line connecting two points on the circle. The point of intersection with the straight to divide the interval into two parts that are equal to each other.

In other words, the video has divided the figure into two equal parts. Point parts of the figure, are located on lines perpendicular to this, are equidistant from it. This direct and will be called the axis of symmetry. Symmetry of this kind is a relatively straight line – is called axial symmetry.

The number of axes of symmetry

Different figures of the number of axes of symmetry will be different. For example, circle and ball these axes a lot. Have an equilateral triangle an axis of symmetry will be the perpendicular on each side, therefore it has three axis. The square and rectangle, it is possible to have four axis of symmetry. Two of them are perpendicular to the sides of the quadrilaterals and the other two are diagonals. But in an isosceles triangle the axis of symmetry, only one, located honey is equal to its sides.

Axial symmetry is found in nature. It can be observed in two ways.

The first type is radial symmetry, assuming the presence of several axes. It is typical, for example, for starfish. More highly developed organisms inherent in bilateral, or bilateral symmetry with one axis, dividing the body into two parts.

The human body is also inherent in bilateral symmetry, but ideally it can not be called. Symmetrically located legs, arms, eyes, lungs, but not heart, liver or spleen. Deviations from bilateral symmetry is noticeable even in appearance. For example, it is extremely rare to have a person on both cheeks was the same birthmark.