Q.
Let z1 and z2 be the nth roots of unity which are ends of a line segment that subtend a right angle at the origin. Then, n must be of the form
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NTA AbhyasNTA Abhyas 2022Complex Numbers and Quadratic Equations
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Solution:
We know that 1n1=cosn2rπ+isinn2rπ,r=0,1,……,n−1
Let, z1=cosn2r1π+isinn2r1π
And, z2=cosn2r2π+isinn2r2π .
Then, ∠z1oz2=amp(z2z1)=amp(z1)−amp(z2) ⇒amp(z1)−amp(z2)=n2(r1−r2)π=2π ∴n=4(r1−r2)=4× integer.
So, n is of the form 4k .