Z1≠Z2 are two points in an argand plane. If a|Z1|=b|Z1|
Prove that aZ1−bZ2aZ1+bZ2 is purely imaginary.
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Solution
Let Z1=r1eiθ,Z2=r2ei(θ+α). Given that ar1=br2 Z=aZ1−bZ2aZ1+bZ2=eiθ−ei(θ+α)eiθ+ei(θ+α) =1−eiα1+eiα (Dividing Nr. and Dr. by eiθ) =e−iα/2−eiα/2e−iα/2+eiα/2 (Dividing Nr. and Dr. by eiα/2) =−2isinα22cosα2 =−itanα2 Hence,Z is purely imaginary Ans: 1