In a plane, a figure rotates a certain angle around a fixed point to get the change of another figure, which is called rotation. This fixed point is called the rotation center, and the rotation angle is called the rotation angle. If point A on the graph rotates to point A', then these two points are called corresponding rotation points.

The rotation of a graph is a positional movement in which each point on the graph moves by a fixed angle around a fixed point on the plane:

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.