【正确答案】(1)S_n1≈S_n=(πmcosγ)/2=(3.1416×2×cos5°06'08")/2mm=3.1291mm≈3.13mm
   h_n1≈m=2mm
   由于S2/2=(πm/2)²，d(2/2)=(mz₂)²，S=πm/2则
   (2)S_n2=S{1-(S2/2)/6d(2/2)}cosγ
   =πm/2{1-(πm/2)²/6(mz₂)²}cosγ
   =(3.1416×2)/2{1-(3.1416×2/2)²/6(2×82)²}cos5°06'08"mm
   =3.1288min≈3.13mm
   h_n2=m+{(s2/2)cos⁴γ}/4d₂
   =2+(3.1416×2/2)²cos5°06'08"/4(2×82)mm
   =2.0148mm≈2.01mm
   S_n1=3.13mm，h_n1=2mm，S_n2=3.13mm，h_n2=2.01mm