弦AB所对圆心角A1=2*ARC SIN((2^0.5/2)/1)=2*ARC SIN(2^0.5/2)=90度
弦AC所对圆心角A2=2*ARC SIN((3^0.5/2)/1)=2*ARC SIN(3^0.5/2)=120度
由AB,AC和弧BC围成地图的面积=PI*R^2*(90+120)/360-R*R/2-R*SIN(120)*R/2
=3.1416*1^2*210/360-1*1/2-1*SIN(120)*1/2
=1.8326-0.5-0.433
=0.9