The smallest angle of rotational symmetry for a square is 90 degrees.
A square has four equal sides and four equal angles, which allows it to be rotated around its center point. When you rotate a square by 90 degrees, it will look exactly the same as it did in its original position. This property holds true for multiples of 90 degrees: after 180 degrees, 270 degrees, and finally 360 degrees, the square will appear unchanged. Therefore, the angles of rotation that result in the square looking the same as its starting position are 90 degrees, 180 degrees, 270 degrees, and 360 degrees, but the smallest of these angles is 90 degrees.