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COMEDK2012MathematicsComplex Number

If a= 2 +i 2 , b= 2 +i 2 , then a b + b a =

Options

  1. A2 i ( - )
  2. B2 isin ( + )
  3. C2 ( + )
  4. D2 ( - )

Correct answer

D. 2 ( - )

Step-by-step solution

We have, a= 2 +i 2 and b= 2 +i 2 a b = Cis 2 Cis 2 = Cis (2 -2 ) So, a b = Cis ( - )= ( - )+i ( - ) and b a = ( - )-i ( - ) Now, a b + b a = ( - )+i ( - )+ ( - )-i ( - )=2 ( - )

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