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Math Help - Min f `(x) d s.t (d^t)d = 1

  1. #1
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    Min f `(x) d s.t (d^t)d = 1

    <br />
\textup{min} f{}'(x)\textup{ }d
     s.t \left \| d \right \|_{2}^{2} = 1
      \textup{show }d = -\frac{f'(x)}{\left \| f(x) \right \|_{2}}
     \textup{my attempt}
     \textup{Let } d = (d_{1}, ... ,d_{n}) <br />
\newline \textup{constraint = } \sum d^{2}_{i}  <br />
\newline \textup{equation = } \sum f'(x)^{2} d^{2}_{i} <br />
\newline \textup{I tryed using lagrangad: using } <br />
L(d, \lambda) = \sum f'(x)^{2} d^{2}_{i}} - \lambda ( \sum d^{2}_{i} - 1) but got the wrong anwser
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  2. #2
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    Dec 2009
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    I don't understand what the equation you are trying to minimize is.
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  3. #3
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    May 2009
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    Quote Originally Posted by NOX Andrew View Post
    I don't understand what the equation you are trying to minimize is.
    Im trying to minimie
    Min f `(x) d s.t (d^t)d = 1-untitled.jpg

    (click on the picture)
    i assmue minmising withrespect to d
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