Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Resonance - from Feynman lectures

  1. Sep 15, 2014 #1
    Good afternoon,

    I am working my way through the Feynman lectures and I am stumped at Chapter 23, Resonance. Specifically, the derivation of equation 23.12. I have followed up to that point but the appearance of tan (theta) baffles me. The equation is below:


    Any help would be greatly appreciated.

  2. jcsd
  3. Sep 15, 2014 #2


    User Avatar

    Staff: Mentor

    You have to use Euler's formula along with a separation of the real and imaginary parts:
    e^{-i \theta} &= \omega_0^2 - \omega^2 + i \gamma \omega \\
    \cos \theta - i \sin \theta &= \omega_0^2 - \omega^2 + i \gamma \omega
    from which you get that ##\cos \theta = \omega_0^2 - \omega^2## and ##\sin \theta = -\gamma \omega##
  4. Sep 15, 2014 #3
    Thanks DrClaude. That's very helpful.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Resonance - from Feynman lectures
  1. The Feynman Lectures (Replies: 12)

  2. Feynman lectures (Replies: 8)