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Concrete mathematics : a foundation for computer science

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9.5 EULER’S SUMMATION FORMULA 461<br />

0((2n)-2”). Of course, we know that this sum is actually a geometric series,<br />

equal to (eb - e”)/(e - 1) = (eb - ea) xkSO Bk/k!.<br />

If f(2m)(x) 3 0 <strong>for</strong> a < x < b, the integral Ji lf(2")(x)l dx is just<br />

f(2m-1)(x)li, so we have<br />

2!.?+yX)~~ B 1 ;<br />

‘R2m’ G (237q!<br />

in other words, the remainder is bounded by the magnitude of the final term<br />

(the term just be<strong>for</strong>e the remainder), in this case. We can give an even better<br />

estimate if we know that<br />

f(2m+2)(x) > 0 and f(2m+41(x) 3 0, <strong>for</strong> a 6 x 6 b. (g-79)<br />

For it turns out that this implies the relation<br />

B2m+2<br />

R2,,, = 8,---<br />

(2m + 2)! f(2m+')(x)l;, <strong>for</strong>someO

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