S阴影=(S△AOD-S扇)+(S圆/4-S△OCD)=[OD*AD/2-πR2(ArcTanAD/OD)/360]+(πR2/4-OC*OD/2)=(3*6/2-3.14*9*63.4/360)+(3.14*9/4-3*3/2)=(9-4.98)+(7.07-4.5)=4.02+2.57=6.59=6.6 cm ...
S阴影=(S△AOD-S扇)+(S圆/4-S△OCD)=[OD*AD/2-πR2(ArcTanAD/OD)/360]+(πR2/4-OC*OD/2)=(3*6/2-3.14*9*63.4/360)+(3.14*9/4-3*3/2)=(9-4.98)+(7.07-4.5)=4.02+2.57=6.59=6.6 cm ...