1/1×2×3+1/2×3×4+…+1/20×21×22
如图,设AC和EF交于点H
那么FH/HE=AF/EC=5/6,
FH=5FE/11=50/11
HE=6FE/11=60/11
S△AHG=1/2×(2+50/11)×10=360/11
S(GHC)=S扇EGC-S△EHC=1/4×π×12×12-1/2×12×60/11=36π-360/11
S求=36π-360/11+360/11=36π≈113.09
求采纳