1. Select the feature points of a known graph (for example, the graph is a trapezoid, and the feature points are its four vertices); 2. Make a line from one of the feature points A to the rotation point O (this step can be omitted if the rotation point is at the feature point); 3. Make a line segment after connecting the required direction and angle (such as 90 degrees clockwise) (such as the feature point is vertex A, the rotation point O is Oa, so that Oa is equal to OA, and the angle with OA is the required angle); 4. Repeat methods 2 and 3 in turn from the next feature point to obtain each line segment; 5. Connect the endpoints of these line segments (point A and point B after the original feature points are rotated) in turn to get the rotated graph.
Refer to the attached drawings.