10.6: F- The Euler-MacLaurin Formula and Asymptotic Series
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You know that a sum can be approximated by an integral. How accurate is that approximation? The Euler-MacLaurin formula gives the corrections.
∑n−1k=0f(k)≈∫n0f(x)dx
−12[f(n)−f(0)]+112[f′(n)−f′(0)]−1720[f′′′(n)−f′′′(0)]+130240[f(v)(n)−f(v)(0)]−11209600[f(vii)(n)
This series is asymptotic. If the series is truncated at any point, it can give a highly accurate approximation. But the series may be either convergent or divergent, so adding additional terms to the truncated series might give rise to a poorer approximation. The Stirling approximation is a truncation of an asymptotic series.
References
C.M. Bender and S.A. Orszag, Advanced Mathematical Methods for Scientists and Engineers, (McGraw-Hill, New York, 1978).
M. Abramowitz and I. Stegum, Handbook of Mathematical Functions, (National Bureau of Standards, Washington, D.C., 1964).