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

Expanding partial derivatives

  1. Jan 28, 2012 #1
    In this textbook, how exactly are 2.2.19 and 2.3.21 equal?

  2. jcsd
  3. Jan 28, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    hi crocomut! :smile:

    standard trick:

    swap i and j … since they're both dummy indices, that gives you the same expression!

    then add, and divide by 2 :wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook