In a plane, a graph rotates around a fixed point by a certain angle to get the change of another graph, which is called graph rotation. This fixed point
It is called the center of rotation and the rotation angle is called the rotation angle.
Properties of graphic rotation:
1, the distance between the corresponding point and the rotation center is equal.
2. The included angle of the connecting line between the corresponding point and the rotation center is equal to the rotation angle.
3. The figures before and after rotation are congruent, that is, the size and shape of the figures before and after rotation have not changed.
4. The rotation center is the only fixed point.
5. The angle of the straight line where the connecting line of a group of corresponding points is located is equal to the rotation angle.
Extended data:
Central symmetry: If a graph can overlap with another graph after rotating 180 degrees around a certain point, then we say these two graphs.
Form a central symmetry.
Centrally symmetric figure: If a figure can overlap itself after rotating 180 degrees around a certain point, then we say that the figure is formed.
Centrally symmetric figure.
The essence of central symmetry:
1. The congruence of two graphs with central symmetry.
2. For two graphs with symmetrical centers, the straight line connecting the symmetrical points passes through the symmetrical center and is equally divided by the symmetrical center. On central symmetry
The corresponding line segments of two graphs are parallel (or on the same straight line) and equal.
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