2π(1.7+R)-2πR=2π*1.7=2*3.14*1.7=10.677m
s=2π(R+1.7)-2πRR为地球半径
3.4π
s=2π(R+1.7)-2πR (R为地球半径) =2π*1.7 =2*3.14*1.7 =10.677m