A.（2-sin1cos1）                      B.sin1cos1

C.R²                                           D.(1-sin1cos1)R²

A.R²                                               B.R²sin2

C.R²                                                         D.（2-sin2）R²

A.R²                                                B.R²sin1·cos1

C. (2-sin1·cos1)R²                         D.R²-sin1·cos1·R²

一个半径为R的扇形，它的周长是4R，则这个扇形中含弓形的面积是

A．

B．

C．

D．

一个半径为R的扇形，它的周长是4R，则这个扇形所含弓形的面积是(    )