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

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•<br />

•<br />

<br />

<br />

<br />

<br />

CR<br />

e iz<br />

z 2 + a<br />

+∞<br />

f(x) dx =<br />

−∞<br />

=<br />

<br />

<br />

dz<br />

2 ≤<br />

+∞<br />

−∞<br />

+∞<br />

−∞<br />

≤<br />

1<br />

R2 − a2 <br />

|e<br />

Cr<br />

iz | |dz| ≤<br />

πR<br />

R2 − a2 R→0<br />

−→ 0 .<br />

cos x<br />

x2 +∞<br />

sin x<br />

dx + i<br />

+ a2 −∞ x2 dx =<br />

+ a2 cos x<br />

x2 dx .<br />

+ a2 <br />

<br />

<br />

+∞<br />

0<br />

cos x<br />

x2 1<br />

dx =<br />

+ a2 2<br />

+∞<br />

−∞<br />

cos x<br />

x2 π<br />

dx =<br />

+ a2 2|a| e−|a| .<br />

|z| = 1<br />

<br />

π<br />

0<br />

cos θ = 1<br />

2 (eiθ + e −iθ ) = 1<br />

2<br />

dθ<br />

a + cos θ<br />

<br />

z + 1<br />

z<br />

<br />

.<br />

2π<br />

1 dθ<br />

=<br />

2 a + cos θ =<br />

= 1<br />

2<br />

= 1<br />

i<br />

<br />

<br />

0<br />

|z|=1<br />

|z|=1<br />

dz (iz) −1<br />

a + 1<br />

2<br />

1 =<br />

(z + z )<br />

dz<br />

z 2 + 2az + 1<br />

α± = −a± √ a 2 − 1 <br />

<br />

Resα+ =<br />

1<br />

α+ − α−<br />

= −Resα− .<br />

<br />

α+ <br />

=<br />

π<br />

√ a 2 − 1 .

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