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-   -   Derivative of function (https://www.askmehelpdesk.com/showthread.php?t=56722)

  • Jan 22, 2007, 08:01 PM
    mld88
    derivative of function
    find derivative of function. Simplify when possible.

    y=xcos^-1x - square root 1-x^2
  • Jan 23, 2007, 07:49 AM
    TechSupport
    The answer is 1.





    I'm lying. Do your own homework.
  • Jan 23, 2007, 08:19 AM
    Capuchin
    I agree with techsupport, although I am happy to give you help with your work, it helps if you ask for help, rather than just demanding at us.

    Secondly, I don't understand your question, what does xcos^-1x mean?
  • Jan 23, 2007, 08:28 AM
    newb
    Capuchin, I believe this person means xarccos(x).

    Phil
  • Jan 23, 2007, 08:43 AM
    Capuchin
    so

    Finding ?

    Hmmm let me have a think.
  • Jan 23, 2007, 11:47 AM
    newb
    the hard part is the derivative of arccos(x). You can either show that for the domain defined by the open unit disc centered on the origin you have arccos(x) = integral from x to 1 of 1/(1 + x^2)^.5 and then use the fundamental thm of calculus (don't forget to switch the limits of integration!) or you can consider theta = arccosx so that d/dx(arccos(x)) = d(theta)/d(cos(theta)) = 1/(-sin(theta)) = -1/(1 - (cos(theta))^2)^.5 = -1/(1 - x^2)^.5.

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