Evaluate the integral above, if it is taken in clockwise direction.
Hint : Use Cauchy Integral.
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The Cauchy Integral takes on the form 2 π i 1 ⋅ ∮ C z − a f ( z ) d z , where C is the unit circle centered at the origin of the complex plane. The above complex integrand can be rewritten as:
3 z − i z 3 − 6 = 3 ( z − i / 3 ) z 3 − 6 = z − i / 3 z 3 / 3 − 2
The pole z = 3 i is contained within C and thus the Cauchy Integral computes to 2 i π f ( a ) = 2 i π f ( i / 3 ) = 2 i π ⋅ ( 3 1 ⋅ ( 3 i ) 3 − 2 ) = 8 1 2 π − 4 i π .