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Question: Answered & Verified by Expert
If z=3+i2 then z101+i103105=
MathematicsComplex NumberAP EAMCETAP EAMCET 2018 (25 Apr Shift 1)
Options:
  • A z
  • B z2
  • C i
  • D -z
Solution:
1747 Upvotes Verified Answer
The correct answer is: i

Given,

z=3+i2

=32+i12

=cosπ6+isinπ6

Then,

z101=cosπ6+isinπ6101

=cos101π6+isin101π6

=cos1016π+isin1016π

=cos17π-π6+isin17π-π6

=-cosπ6+isinπ6 

=-3+i2

And, i103=i4×25+3=i3=-i

Therefore,

z101+i103105=-32+i2-i105

=-32-i2105

=-3+i2105

=-z105

Now,

-z105=-3+i2105

                =-cosπ6+isinπ6105

=-cos105π6+isin105π6

=-cos18π-3π6+isin18π-3π6

 =-cos3π6-isin3π6

 =-cosπ2-isinπ2

 =--i

=i

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