Let z1,z2,z3 be three points on |z|=1.If Θ1,Θ2,Θ3 be the arguments of z1,z2,z3 respectively then cos(Θ1-Θ2)+cos(Θ2-Θ3)+cos (Θ3-Θ1)
a. >=-3/2
b. <=-3/2
c.>=3/2
d. none

Dear Vaibhay

In the question nothing is given about Θ1,Θ2,Θ3

so choose any value of Θ1,Θ2,Θ3

let Θ1,Θ2,Θ3 are nearly equal so

 (Θ1-Θ2)≈0

(Θ2-Θ3)≈0

 (Θ3-Θ1)≈0

so cos(Θ1-Θ2)+cos(Θ2-Θ3)+cos (Θ3-Θ1) ≈3

option a and c are correct

similerly we can choose other angel also

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