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AP EAMCET202119 Aug 2021Morning ShiftMathematicsComplex NumberActual

Real part of ( cos 4 + i sin 4 + 1 ) 2020 is_______

Options

  1. A2 2020 cos 2020 ⁡ 2 cos ⁡ 2020
  2. B2 2020 cos 2020 ⁡ 2 cos ⁡ 4040
  3. C2 1020 cos 2020 ⁡ 2 cos ⁡ 4040
  4. D2 2020 cos 2020 ⁡ 1 cos ⁡ 2020

Correct answer

B. 2 2020 cos 2020 ⁡ 2 cos ⁡ 4040

Step-by-step solution

Given, ( cos 4 + i sin 4 + 1 ) 2020 Now using, 1 + cos 2 A = 2 cos 2 A and sin 2 A = 2 sin A cos A , we get 2 cos 2 2 + 2 i sin 2 cos 2 2020 ⇒ 2 cos 2 cos 2 + i sin 2 2020 Now, By using De Moivre's Theorem, we get ⇒ 2 2020 cos 2020 2 cos 2 × 2020 + i sin 2 × 2020 ⇒ 2 2020 cos 2020 2 cos 4040 + i sin 4040 Hence, the Real part is 2 2020 cos 2020 2 cos 4040

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