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MCS 351 ENGINEERING MATHEMATICS SOLUTION OF ...

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g(z) =<br />

sinh πz<br />

z 2 − 3z<br />

=<br />

sinh πz<br />

z(z − 3)<br />

Singular points of g are z 0 = 0 and z 1 = 3. Let D be the union of C and the interior part of C. Then<br />

z 1 = 3 /∈ D but z 0 = 0 ∈ D. f(z) =<br />

we get<br />

12.<br />

∮<br />

C<br />

∮<br />

g(z)dz =<br />

C<br />

sinh πz<br />

z−3<br />

is analytic in D. Hence by use of Cauchy integral formula,<br />

sinh πz<br />

z − 3 .1 0<br />

dz = 2πi.f(0) = 2πisinh<br />

z −3<br />

= 2π sin(i.0) = 0<br />

−3<br />

Let g(z) = tan z<br />

z−i . Singular point z 0 = i is enclosed by C. f(z) = tan z is analytic in D when D is the<br />

union of C and the interior part of C. So by the use of Cauchy integral formula, we get<br />

∮<br />

tan z<br />

dz = 2πi tan i<br />

z − i<br />

13.<br />

C<br />

g(z) = e−3πz 1<br />

2z + i = 2 e−3πz<br />

z + i 2<br />

Singular point z 0 = − i 2 is enclosed by C. f(z) = 1 2 e−3πz is analytic in D when D is the union of C and<br />

the interior part of C. So by use of Cauchy integral formula, we get<br />

∮<br />

e −3πz<br />

1<br />

2z + i<br />

∮C<br />

dz = dz = 2πi. 1 2 e− 3 2 πi =<br />

2 e−3πz<br />

C<br />

z + i 2<br />

15. We sketch C : |z − 4| = 2 as follows:<br />

41<br />

πi<br />

3<br />

2 (cos π + i sin π) = −2 3 πi

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