First question: perimeter is the perimeter of a sector.

The second question:

1, connecting OD, we can know that OBD is an equilateral triangle, and the angle OBC=30 degrees is obtained by folding;

2. From a 30-degree right triangle, the length of each side can be found, and the OBC area of the triangle can be found, and then multiplied by 2, the blank area can be obtained;

3. Use sector area-blank area = shadow area.