1, first take a square piece of paper, fold it in half in all directions and then fold it horizontally, and draw a quarter circle with compasses, with a small square as the radius. Then cut it along the line with scissors, unfold the paper and open it along the line where it was just folded, so that the four sectors will be fine. Cut along the scissors

2. A sector is an arc, and the figure surrounded by two radii passing through both ends of the arc is called a sector (the combination of semicircle and diameter is also a sector). Obviously, it is surrounded by a part of the circumference and its corresponding central angle. In Elements of Geometry, a sector is defined as a figure surrounded by two sides of an angle whose vertex is in the center of a circle and is cut into an arc by these two sides.