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Math Help - Derivative simplification.

  1. #1
    Senior Member
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    Derivative simplification.

    I'm not sure how to get from one expression to another.

    According to maxima, the partial derivative of: <br />
\frac{x}{\sqrt{x^2+y^2+z^2}}<br />
w.r.t x is:
    Code:
    (%i7) diff(x/(sqrt(x^2+y^2+z^2)),x);
                                                                     2
                                                1                   x
    (%o7)                               ------------------ - -----------------
                                              2    2    2      2    2    2 3/2
                                        sqrt(z  + y  + x )   (z  + y  + x )
    Which makes sense to me, but Maple somehow managed to simplify it to the following, which I don't know how they did:


    Only the second term is what I'm interested in, as that is what differs.

    Thanks.
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  2. #2
    MHF Contributor
    Joined
    Nov 2008
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    France
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    1,458
    Quote Originally Posted by scorpion007 View Post
    I'm not sure how to get from one expression to another.

    According to maxima, the partial derivative of: <br />
\frac{x}{\sqrt{x^2+y^2+z^2}}<br />
w.r.t x is:
    Code:
    (%i7) diff(x/(sqrt(x^2+y^2+z^2)),x);
                                                                     2
                                                1                   x
    (%o7)                               ------------------ - -----------------
                                              2    2    2      2    2    2 3/2
                                        sqrt(z  + y  + x )   (z  + y  + x )
    Which makes sense to me, but Maple somehow managed to simplify it to the following, which I don't know how they did:


    Only the second term is what I'm interested in, as that is what differs.

    Thanks.
    Hi

    The difference comes from the fact that your input for Maple is not correct since you forgot the square root
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  3. #3
    Senior Member
    Joined
    Jul 2006
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    364
    Ahh! Haha. Of course! Thanks for catching that
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