complex geometry

If mod(z)=1, then prove that the points represented by√(1+z)/(1-z) lie on one or other of two fixed perpendicular lines

7 Answers

1
Ashish Sharma ·

By √(1+z)/(1-z) you mean √(1+z)/(1-z) or √(1+z) / (1-z) ??

24
eureka123 ·

(1+z)/(1-z)

24
eureka123 ·

help.......

62
Lokesh Verma ·

(1+z)/(1-z)

subst z=eiθ

(1+z)/(1-z) = (1+cosθ+isinθ)/(1-cosθ-isinθ)

in the numerator, cosθ=2sin2θ/2-1
in the denominaotr, cosθ=1-2cos2θ/2
also, sinθ=2sinθ/2.cosθ/2

we get 1+z/1-z= {cosθ/2.(cosθ/2+isinθ/2)}/{sinθ/2(sinθ/2-icosθ/2)}

see carefully the RHS gets reduced to cotθ/2.i

62
Lokesh Verma ·

Thus, √(1+z)/(1-z) = √cot(θ/2) . √i

so square root fo i will have two roots.. one will be 1/√2+1/√2i and -1/√2-1/√2i

I have no clue what mistake i am making.. but i guess someone who can find the mistake in this question? !

33
Abhishek Priyam ·

ye mai bhi laya... par misyake kaha hain...

I have no clue what mistake i am making.. but i guess someone who can find the mistake in this question? !

62
Lokesh Verma ·

so what we can say is that the two roots of i are perpendicular

isnt it?

the slopes are 1 and -1

:)

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