Complex numbers on unit circle

  • Thread starter treetheta
  • Start date
  • #1
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Homework Statement


Let z1; z2; z3; z4 be four complex numbers on the unit circle (i.e., |z1|=|z2|=|z3|=|z4|=1).
It is known that z1+z2+z3+z4=1+i . Find the value of
1/z1
+
1/z2
+
1/z3
+
1/z4




Homework Equations



1/z = barZ/|z|^2

The Attempt at a Solution



I've been trying for about a day now and i just have no clue absolutely, I understand that
[b -a]/ [ab] = [1/a] - [1/b]

but i think there's something to do with conjugates or something this question is quite fustrating.

i also tried letting z1 + z2 + z3 + z4 = w
and then w*(barW) but i just got 0(1+i)(1-i) and then i cant take the inverse
 
Last edited:

Answers and Replies

  • #2
22,089
3,297
So you know

[tex]z_1+z_2+z_3+z_4=1+i[/tex]

What if you take the conjugate of both sides?
 
  • #3
dynamicsolo
Homework Helper
1,648
4
Have you had DeMoivre's Theorem? You know that all of the z's have unit modulus. What would 1/z equal for each z ?
Draw the z's and (1/z)'s on an Argand diagram. How does the sum of the (1/z)'s relate to the sum of the z's ?
 

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