Use the de Moivre theorem to evaluate the following: \frac{(1+i)(\sqrt{3}+i)^3}{(1-\sqrt{3}i)^3}=1-i

Phoebe Xiong

Phoebe Xiong

Answered question

2022-02-26

Use the de Moivre theorem to evaluate the following:
(1+i)(3+i)3(13i)3=1i

Answer & Explanation

aksemaktjya

aksemaktjya

Beginner2022-02-27Added 6 answers

1+i=2(cos(π4)+isin(π4))
3+i=2(cos(π6)+isin(π6))
1i3=2(cos(π3)+isin(π3)
Then you can simply apply De Moivre's theorem:
The numerator becomes 82(cos(9π12)+isin(9π12))=82(cos(3π4)+isin(3π4))
The denominator becomes 8(cos(π)+isin(π))=8
So the fraction is equal to 2(cos(3π4)+isin(3π4))=1i

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