1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Differentiate the law of Cosine

  1. Jan 29, 2008 #1
    It is a simple math question, but I am stuck.

    The law of cosines is

    R^2=h^2 + r^2 - 2 h r cos (theta). Theta is of course the angle facing R.

    To differentiate, I first set

    r^2 - 2hr cos[tex]\Theta[/tex]+ (h^2-R^2) = 0

    2 r [tex]\dot{}r[/tex] - 2 h cos[tex]\Theta[/tex] [tex]\dot{}r[/tex] + (h^2-R^2) = 0.

    Is there any way to put h^2-R^2 in terms of [tex]\dot{}\theta[/tex] or d[tex]\theta[/tex]/dt
  2. jcsd
  3. Jan 29, 2008 #2
    Arr, nevermind. I got it.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Differentiate the law of Cosine
  1. Cosine law (Replies: 3)