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

Implicit differentiation in multiple variables

  1. Mar 20, 2013 #1
    So, as the title may have given away, I'm trying to figure out implicit differentiation in the multiple variable context. I thought a good practice would be the law of cosines, aka
    c^2 = a^2 + b^2 - 2abcosθ.
    So I'm trying to find ∂θ/∂a, ∂θ/db, ∂θ/dc.
    I tried solving for θ and then taking partials, but that seems like the wrong way to do it. Any suggestions?
  2. jcsd
  3. Mar 20, 2013 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Solve for ##\cos\theta## and use the chain rule to express, say, ##\partial \theta/\partial a## in terms of ##\partial (\cos \theta)/\partial a##. You can use a trig identity to rewrite the sin function in terms of the original cos.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Implicit differentiation in multiple variables
  1. Implicit Differentiation (Replies: 18)

  2. Implicit Differentiation (Replies: 12)