Answer:
10.5 cm
Step-by-step explanation:
Since we know that O lies on AB we know that:
- The distance from the midpoint of OA to O is 6 cm (12/2).
- The distance from the midpoint of OB to O is 4.5 cm (9/2).
You can add 6 to 4.5 to get 10.5 cm.
When we rotate a figure and there is no change in the shape of the figure then it has rotational symmetry.
We know that the order of rotation for a square is 4.
Hence, we have 
Thus, the angle of rotational symmetry of square are

Hence, the minimum angle of rotational symmetry is 
Therefore, the minimum angle of rotational symmetry for a square is 90 degrees.
The original price was $64
Hope this helps:)