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The Real And Complex Number Systems

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and<br />

f 0 (x) =<br />

n=0<br />

∞∑<br />

n=0<br />

P n (0) xn<br />

n! = x<br />

e x − 1 .<br />

So, we have the identity<br />

∞∑<br />

P n (t) xn<br />

n! = ∑ ∞ etx P n (0) xn<br />

n! .<br />

n=0<br />

Use the identity with e tx = ∑ ∞ t n<br />

n=0 n! xn , then we obtain<br />

n∑<br />

which implies that<br />

P n (t)<br />

n!<br />

=<br />

k=0<br />

= 1 n!<br />

P n (t) =<br />

t n−k P k (0)<br />

(n − k)! k!<br />

n∑<br />

( n k) P k (0) t n−k<br />

k=0<br />

n∑<br />

( n k) P k (0) t n−k .<br />

k=0<br />

This shows that each function P n is a polynomial. <strong>The</strong>re are the Bernoulli<br />

polynomials. <strong>The</strong> numbers B n = P n (0) (n = 0, 1, 2, ...) are called the<br />

Bernoulli numbers. Derive the following further properties:<br />

(c) B 0 = 1, B 1 = − 1 2 , ∑ n−1<br />

k=0 (n k ) B k = 0, if n = 2, 3, ...<br />

Proof: Since 1 = p(x) , where p (x) := ∑ ∞ x n<br />

p(x) n=0<br />

, and 1 := ∑ ∞<br />

(n+1)! p(x) n=0 P n (0) xn . n!<br />

So,<br />

where<br />

1<br />

1 = p (x)<br />

p (x)<br />

∞∑ x n<br />

=<br />

(n + 1)!<br />

n=0<br />

∞∑<br />

= C n x n<br />

C n =<br />

n=0<br />

1<br />

(n + 1)!<br />

n∑<br />

k=0<br />

36<br />

∞∑<br />

n=0<br />

P n (0) xn<br />

n!<br />

( n+1<br />

)<br />

k Pk (0) .

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