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Need a little help with a derivative problem please

  1. Oct 9, 2009 #1
    If f(x) = 7sin(3 x) * (arcsin(x)), find f'( x ).


    I'm assuming I need to use the product rule, but I am failing to set it up right. I assume it's with the beginning part and I'm just goofing up on what to do with the coefficient.

    I think it's ((7sin3x)' * arcsinx) + (7sin(3x) + 1/(sqrt(1-x^2)).

    If that's correct I'm just failing to get the derivative. I can't seem to remember how I should proceed with something in that form. I should be past this but I'm having trouble seeing it. Any help would be great.

    Thank you
     
  2. jcsd
  3. Oct 9, 2009 #2

    LCKurtz

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    Your last + should be multiplication.
     
  4. Oct 9, 2009 #3
    Ah yes it is I just typed it up wrong in my initial post. I cant seem to figure out the derivative though. The derivative of 7sin3x is not working out for me. I tried things like 7cos3x(3) but that doesnt seem to work. Any help would be great thanks
     
  5. Oct 9, 2009 #4

    Dick

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    I don't see anything wrong with 21*cos(3x) as the derivative of 7*sin(3x).
     
  6. Oct 9, 2009 #5
    so would the final answer be

    21cos3x(arcsinx)+(7sin3x)/(sqrt(1-x^2))


    because that does not seem to be the right answer on my web assignment i dunno
     
  7. Oct 9, 2009 #6

    Dick

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    I can't really speak for web assignment, but it looks ok to me.
     
  8. Oct 9, 2009 #7
    Ok thanks much for your help perhaps there is a problem with the program.
     
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