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AP EAMCET · Maths · Complex Number

If a=cos8π11+isin8π11, then Rea+a2+a3+a4+a5=

  1. A 0
  2. B -12
  3. C 12
  4. D 1
Verified Solution

Answer & Solution

Correct Answer

(B) -12

Step-by-step Solution

Detailed explanation

We have, a=cos8π11+isin8π11 Then, a2=cos8π11+isin8π112 =cos16π11+isin16π11 a3=cos24π11+isin24π11 a4=cos32π11+isin32π11 a5=cos40π11+isin40π11 Now, =a+a2+a3+a4+a5…