Given that |z−1|=1, where z is a point on the Argand plane. Find z−2z
A
−itan(argz)
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B
tan(argz)
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C
−tan(argz)
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D
itan(argz)
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Solution
The correct option is Ditan(argz) We have |z−1|=1 Let z−1=cosθ+isinθ ∴z−2=cosθ+isinθ−1 =−2sin2θ/2+2isinθ/2cosθ/2 z−2=2isinθ/2(cosθ/2+isinθ/2) ........ (1) and z=1+cosθ+isinθ =2cos2θ/2+2isinθ/2cosθ/2 z=2cosθ/2(cosθ/2+isinθ/2) ....... (2) from (1) and (2) z−2z=itanθ/2 =itan(argz) (∵argz=θ/2 from (2)) Ans: D