设大圆、小圆半径分别是R、r厘米.
连接OA、OB、O1F.
OA=OB=R,O1F = r
做OE垂直于AB于E点.OE垂直平分AB.
显然OE∥O1F
又因为AB∥CD
所以OE = O1F = r
又OA^2 = OE^2 + AE^2 = OE^2 + (AB/2)^2
即R^2 = r^2 + 4
R^2 - r^2 = 4
阴影部分面积
= πR^2 /2 - πr^2 /2
= π(R^2 - πr^2)/2
= 2π
设大圆、小圆半径分别是R、r厘米.
连接OA、OB、O1F.
OA=OB=R,O1F = r
做OE垂直于AB于E点.OE垂直平分AB.
显然OE∥O1F
又因为AB∥CD
所以OE = O1F = r
又OA^2 = OE^2 + AE^2 = OE^2 + (AB/2)^2
即R^2 = r^2 + 4
R^2 - r^2 = 4
阴影部分面积
= πR^2 /2 - πr^2 /2
= π(R^2 - πr^2)/2
= 2π