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Math Help - Partial Derivative

  1. #1
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    Exclamation Partial Derivative

    hi everyone,

    im trying to do the partial derivate of x^tAx ..please could you see the image? it will make more sense

    what i dont know is how they got the partial derivative. and why is it 2a(ii). how did it change to a(ii) from a(ij)

    i hope it's clear and Thank you very much everyone
    Attached Thumbnails Attached Thumbnails Partial Derivative-maths.jpg  
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  2. #2
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    Quote Originally Posted by matlabnoob View Post
    hi everyone,

    im trying to do the partial derivate of x^tAx ..please could you see the image? it will make more sense

    what i dont know is how they got the partial derivative. and why is it 2a(ii). how did it change to a(ii) from a(ij)
    Are you aware the a_{ii} are the diagnal elements of A?

    Also x^tAx is a quadratic form.
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  3. #3
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    Quote Originally Posted by pickslides View Post
    Are you aware the a_{ii} are the diagnal elements of A?

    Also x^tAx is a quadratic form.

    i am aware of this, but still do not understand how the partial derivative is done. i thought all you do is ignore the other terms, look at x(i) so you get the sum of a(ij)*x(i) ? but this is not the case here?
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