i know it's supposed to be a simple question. frustrating because it is not coming to me. just want a hint.(adsbygoogle = window.adsbygoogle || []).push({});

question is:

how do you write

1 + cos(theta) + cos (2*theta) + cos(3*theta).... cos(n*theta) using the fact that (z^(n+1) -1) / (z^(n) -1) = 1 + z + z^(2) +... + z^(n)

thanks in advance

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Complex analysis question (only need a hint)

**Physics Forums | Science Articles, Homework Help, Discussion**