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    ankara55t's Avatar
    ankara55t Posts: 53, Reputation: 2
    Junior Member
    		  
    #1

    Oct 26, 2009, 04:02 PM
    trigonometry derivative confusion
    In finding the derivative of g(x) = (cosx)^3

    we get, g'(x) = 3(cosx)^2(-sinx)

    but I don't understand how this can be simplified to

    g'(x) = -3cos^2xsinx Why is is permissible to move the power of 2 to be immediately after cos instead of
    after cosx?
    s_cianci's Avatar
    s_cianci Posts: 5,472, Reputation: 760
    Uber Member
    		  
    #2

    Oct 26, 2009, 04:13 PM
    It's simply a notational thing that's commonly used with trigonometric functions. Cos^2 is understood to mean the same as (cos x)^2, so as not to be confused with cos (x^2).
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