扇形面积公式s=n/360r1*r1*3.14圆面积公式s=r2*r2*3.14扇型面积和园的面积相等即r2*r2*3.14=n/360r1*r1*3.14r1=2r2r2*r2=n/360*4*r2*r2n/360*4=1n=90
180
