一个扇形的面积为S=6π，它的弧长为C=2π，求圆心角A及半径R?C=R*A=2πA=2*π/RS=π*R^2*A/(2*π) =R^2*A/2 =R^2*2*π/2 =R^2*π =6πR^2=6R=6^0.5=2.449A=2*π/R =2*π/2.449 =0.816497*π弧度 =0.816497*π*180/π =146.97度
