Consider the regular pentagon ABCDE, with center (of mass) O.
The central angle O is a complete angle, so its measure is 360°.
It is divided into 5 equal parts, so each of them has a measure of 360°/5=72°.
If we rotate the pentagon, with point O as the center of the rotation, we can map A to any of the other points.
The smallest angle of rotation is the angle which mas A to E, 72°.
Answer: 72°