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For a complex number Z , if arg Z ∈ - π , π , then arg 1 + cos ⁡ 6 π 7 + i sin ⁡ 6 π 7 is (here i 2 = - 1 )

Options

  1. A3 π 7
  2. B2 π 7
  3. C- 2 π 7
  4. D- 3 π 7

Correct answer

A. 3 π 7

Step-by-step solution

Let W = 1 + cos ⁡ 6 π 7 + i sin ⁡ 6 π 7 = 2 cos ⁡ 3 π 7 cos ⁡ 3 π 7 + i sin ⁡ 3 π 7 Hence, arg W = 3 π 7

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