因为e约等于2.718,与3接近,√3约等于1.732
√e=√(3-(3-e))=√3*(1-(3-e)/3)^(1/2)
=√3*(1-(1/2)*(3-e)/3+1/8*{(3-e)/3}^2+.
=1.732*(1-0.047+0.001)=1.732*0.954=1.6523