我的算法是一个扇形面积加上两个三角形面积,再减去另一个扇形面积。
http://duping.net/XHC/data/uploads/8/7670/7670_323.PNG
http://duping.net/XHC/data/uploads/8/7670/7670_324.PNG
http://duping.net/XHC/data/uploads/8/7670/7670_323.PNG
http://duping.net/XHC/data/uploads/8/7670/7670_324.PNG