1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Derivatives product rule help

  1. Nov 11, 2009 #1
    1. The problem statement, all variables and given/known data
    find the dy/dx of y= 4- x (to the 2nd power) sin x

    2. Relevant equations
    is there a rule?

    3. The attempt at a solution
  2. jcsd
  3. Nov 11, 2009 #2
    Re: derivatives

    Is it 4 - (x^2*sin(x)) or ((4-x)^2 * sin(x))?

    You will need the product rule for the first case, or for the second case a combination of the product rule and the chain rule.

    Product rule: f'(x) * g(x) + g'(x) * f(x)
    Chain rule: f'(g(x)) * g'(x)
  4. Nov 11, 2009 #3
    Re: derivatives

    Ok, per the visitor message I got from you..you don't understand how to use the product rule.

    Use the following information:
    Let f(x) = x^2 and g(x) = sin(x). The derivative of sin(x) is cos(x) - memorize this. Use the power rule for the derivative of x^2.

    f'(x) refers to the derivative of f(x), and g'(x) refers to the derivative of g(x). You should now be able to use the product rule to calculate the derivative.

    If you need more help someone else will have to help you, I have to leave now.
  5. Nov 11, 2009 #4
    Re: derivatives

    thank you very much
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook