Then take this as the edge and use the protractor as the angle (clockwise to the right and counterclockwise to the left)

After completion, measure the distance from the previously selected vertex A to the rotation center O..

Then set this distance to the other side of the angle you made (that is, the one you drew) and find out the position of point D. At this time,

D is the corresponding point of a after rotation.

Graphics, how many vertices do this, one after another.

Finally, all the corresponding points are found out, and then they can be connected.