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Esercizi svolti di analisi reale e complessa - Dipartimento di ...

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1 <br />

n −n <br />

∞<br />

<br />

sin πz = πz<br />

.<br />

<br />

n≥2<br />

<br />

1 − 1<br />

n2 <br />

n=1<br />

<br />

1 − z2<br />

n 2<br />

sin πz<br />

= lim<br />

z→1 πz(1 − z)(1 + z) =<br />

= 1<br />

2 lim<br />

sin π(1 − z) 1<br />

=<br />

z→1 π(1 − z) 2 .<br />

<br />

cos θ = 1<br />

<br />

1<br />

2 z + z |z| =<br />

1<br />

2π<br />

(cos θ) 2n dθ =<br />

0<br />

=<br />

1<br />

22n <br />

1<br />

i2 2n<br />

S 1<br />

<br />

S 1<br />

<br />

z + 1<br />

2n dz =<br />

z<br />

(z 2 + 1) 2n<br />

z 2n+1<br />

0 2n + 1 <br />

Res0 = D2n z (z2 + 1) 2n<br />

.<br />

2n! |z=0<br />

<br />

<br />

(1 + z 2 ) 2n =<br />

<br />

Res0 =<br />

2n<br />

j=0<br />

2n<br />

n<br />

2n<br />

j<br />

<br />

.<br />

2π<br />

(cos θ)<br />

0<br />

2n dθ = . . . = 1<br />

i22n <br />

= 2πi<br />

22ni =<br />

<br />

2n<br />

n<br />

<br />

<br />

S 1<br />

<br />

z 2j<br />

dz .<br />

(z 2 + 1) 2n<br />

z2n+1 dz =<br />

<br />

(2n − 1)!!<br />

= 2π<br />

2n!!

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