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Math Help - Trigonometric Differentiation

  1. #1
    mortoleeuk
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    Question Trigonometric Differentiation

    hi,

    here y = 3xsinx

    dy/dx = 3sinx + 3xcosx

    could someone run through the process of getting that, exam 2moro...Thanx
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  2. #2
    hpe
    hpe is offline
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    Apr 2005
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    Quote Originally Posted by mortoleeuk
    hi,

    here y = 3xsinx

    dy/dx = 3sinx + 3xcosx

    could someone run through the process of getting that, exam 2moro...Thanx
    Use the product rule (uv)' = u'v + uv', with u = 3x and v = sin(x) such that uv = 3xsin(x).
    Then u' = 3 and v' = cos(x).
    Thus u'v = 3sin(x) and uv' = 3xcos(x).
    Thus dy/dx = (uv)' = u'v + uv' = 3sin(x) + 3xcos(x).
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