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

Homework Help: Simplifying wrong or completely wrong?

  1. Nov 16, 2011 #1
    1. The problem statement, all variables and given/known data
    Find dy/dx.

    2. Relevant equations

    3. The attempt at a solution
    Using the chain rule,


    Answer is:

    What am I missing here ?
  2. jcsd
  3. Nov 16, 2011 #2


    Staff: Mentor

    Your answer is correct, and so is the other answer you show. They are using the identity sin(2A) = 2sin(A)cos(A). In your problem A = 3x - 2.
  4. Nov 16, 2011 #3


    User Avatar
    Homework Helper

    The identity

  5. Nov 16, 2011 #4
    Ah, I remember that now, now I'll remember that identity, thank you.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook