Simplify Derivative with Substitution

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3
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I try to evaluate:



$$ fracpartialpartial x logu(x, y, z)$$



Mathematica gives:



$$ frac1x+y+z$$



I want to simplify the expression with my function:



$$ frac1u(x, y, z)$$



How to do that?



Thanks.



u[x_, y_, z_] = x + y + z
Simplify[D[Log[u[x, y, z]], x]]









share|improve this question

























    up vote
    3
    down vote

    favorite












    I try to evaluate:



    $$ fracpartialpartial x logu(x, y, z)$$



    Mathematica gives:



    $$ frac1x+y+z$$



    I want to simplify the expression with my function:



    $$ frac1u(x, y, z)$$



    How to do that?



    Thanks.



    u[x_, y_, z_] = x + y + z
    Simplify[D[Log[u[x, y, z]], x]]









    share|improve this question























      up vote
      3
      down vote

      favorite









      up vote
      3
      down vote

      favorite











      I try to evaluate:



      $$ fracpartialpartial x logu(x, y, z)$$



      Mathematica gives:



      $$ frac1x+y+z$$



      I want to simplify the expression with my function:



      $$ frac1u(x, y, z)$$



      How to do that?



      Thanks.



      u[x_, y_, z_] = x + y + z
      Simplify[D[Log[u[x, y, z]], x]]









      share|improve this question













      I try to evaluate:



      $$ fracpartialpartial x logu(x, y, z)$$



      Mathematica gives:



      $$ frac1x+y+z$$



      I want to simplify the expression with my function:



      $$ frac1u(x, y, z)$$



      How to do that?



      Thanks.



      u[x_, y_, z_] = x + y + z
      Simplify[D[Log[u[x, y, z]], x]]






      calculus-and-analysis simplifying-expressions






      share|improve this question













      share|improve this question











      share|improve this question




      share|improve this question










      asked Nov 22 at 17:33









      R zu

      1797




      1797




















          2 Answers
          2






          active

          oldest

          votes

















          up vote
          7
          down vote



          accepted










          D[Log[u[x, y, z]], x] /. u[x_, y_, z_] :> Defer[u[x, y, z]]



          1/u[x, y, z]







          share|improve this answer






















          • A more general substitution: /. u[x_,y_,z_] -> Defer[u[x,y,z]]
            – R zu
            Nov 22 at 18:04










          • @Rzu, good point.
            – kglr
            Nov 22 at 18:05

















          up vote
          4
          down vote













          An alternative is to define UpValues instead of DownValues of u:



          Derivative[1, 0, 0][u] ^:= 1&
          Derivative[0, 1, 0][u] ^:= 1&
          Derivative[0, 0, 1][u] ^:= 1&

          D[Log[u[x, y, z]], x]



          1/u[x, y, z]







          share|improve this answer




















          • What are UpValues and DownValues? The definition in the doc seems recursive: UpValue "gives a list of transformation rules corresponding to all upvalues defined for the symbol f. "
            – R zu
            Nov 22 at 19:29











          • @Rzu Maybe you can check out the documentation for UpSetDelayed and TagSetDelayed.
            – Carl Woll
            Nov 22 at 19:39











          Your Answer





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          2 Answers
          2






          active

          oldest

          votes








          2 Answers
          2






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          7
          down vote



          accepted










          D[Log[u[x, y, z]], x] /. u[x_, y_, z_] :> Defer[u[x, y, z]]



          1/u[x, y, z]







          share|improve this answer






















          • A more general substitution: /. u[x_,y_,z_] -> Defer[u[x,y,z]]
            – R zu
            Nov 22 at 18:04










          • @Rzu, good point.
            – kglr
            Nov 22 at 18:05














          up vote
          7
          down vote



          accepted










          D[Log[u[x, y, z]], x] /. u[x_, y_, z_] :> Defer[u[x, y, z]]



          1/u[x, y, z]







          share|improve this answer






















          • A more general substitution: /. u[x_,y_,z_] -> Defer[u[x,y,z]]
            – R zu
            Nov 22 at 18:04










          • @Rzu, good point.
            – kglr
            Nov 22 at 18:05












          up vote
          7
          down vote



          accepted







          up vote
          7
          down vote



          accepted






          D[Log[u[x, y, z]], x] /. u[x_, y_, z_] :> Defer[u[x, y, z]]



          1/u[x, y, z]







          share|improve this answer














          D[Log[u[x, y, z]], x] /. u[x_, y_, z_] :> Defer[u[x, y, z]]



          1/u[x, y, z]








          share|improve this answer














          share|improve this answer



          share|improve this answer








          edited Nov 22 at 18:05

























          answered Nov 22 at 17:36









          kglr

          173k8196401




          173k8196401











          • A more general substitution: /. u[x_,y_,z_] -> Defer[u[x,y,z]]
            – R zu
            Nov 22 at 18:04










          • @Rzu, good point.
            – kglr
            Nov 22 at 18:05
















          • A more general substitution: /. u[x_,y_,z_] -> Defer[u[x,y,z]]
            – R zu
            Nov 22 at 18:04










          • @Rzu, good point.
            – kglr
            Nov 22 at 18:05















          A more general substitution: /. u[x_,y_,z_] -> Defer[u[x,y,z]]
          – R zu
          Nov 22 at 18:04




          A more general substitution: /. u[x_,y_,z_] -> Defer[u[x,y,z]]
          – R zu
          Nov 22 at 18:04












          @Rzu, good point.
          – kglr
          Nov 22 at 18:05




          @Rzu, good point.
          – kglr
          Nov 22 at 18:05










          up vote
          4
          down vote













          An alternative is to define UpValues instead of DownValues of u:



          Derivative[1, 0, 0][u] ^:= 1&
          Derivative[0, 1, 0][u] ^:= 1&
          Derivative[0, 0, 1][u] ^:= 1&

          D[Log[u[x, y, z]], x]



          1/u[x, y, z]







          share|improve this answer




















          • What are UpValues and DownValues? The definition in the doc seems recursive: UpValue "gives a list of transformation rules corresponding to all upvalues defined for the symbol f. "
            – R zu
            Nov 22 at 19:29











          • @Rzu Maybe you can check out the documentation for UpSetDelayed and TagSetDelayed.
            – Carl Woll
            Nov 22 at 19:39















          up vote
          4
          down vote













          An alternative is to define UpValues instead of DownValues of u:



          Derivative[1, 0, 0][u] ^:= 1&
          Derivative[0, 1, 0][u] ^:= 1&
          Derivative[0, 0, 1][u] ^:= 1&

          D[Log[u[x, y, z]], x]



          1/u[x, y, z]







          share|improve this answer




















          • What are UpValues and DownValues? The definition in the doc seems recursive: UpValue "gives a list of transformation rules corresponding to all upvalues defined for the symbol f. "
            – R zu
            Nov 22 at 19:29











          • @Rzu Maybe you can check out the documentation for UpSetDelayed and TagSetDelayed.
            – Carl Woll
            Nov 22 at 19:39













          up vote
          4
          down vote










          up vote
          4
          down vote









          An alternative is to define UpValues instead of DownValues of u:



          Derivative[1, 0, 0][u] ^:= 1&
          Derivative[0, 1, 0][u] ^:= 1&
          Derivative[0, 0, 1][u] ^:= 1&

          D[Log[u[x, y, z]], x]



          1/u[x, y, z]







          share|improve this answer












          An alternative is to define UpValues instead of DownValues of u:



          Derivative[1, 0, 0][u] ^:= 1&
          Derivative[0, 1, 0][u] ^:= 1&
          Derivative[0, 0, 1][u] ^:= 1&

          D[Log[u[x, y, z]], x]



          1/u[x, y, z]








          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered Nov 22 at 19:26









          Carl Woll

          65.9k285171




          65.9k285171











          • What are UpValues and DownValues? The definition in the doc seems recursive: UpValue "gives a list of transformation rules corresponding to all upvalues defined for the symbol f. "
            – R zu
            Nov 22 at 19:29











          • @Rzu Maybe you can check out the documentation for UpSetDelayed and TagSetDelayed.
            – Carl Woll
            Nov 22 at 19:39

















          • What are UpValues and DownValues? The definition in the doc seems recursive: UpValue "gives a list of transformation rules corresponding to all upvalues defined for the symbol f. "
            – R zu
            Nov 22 at 19:29











          • @Rzu Maybe you can check out the documentation for UpSetDelayed and TagSetDelayed.
            – Carl Woll
            Nov 22 at 19:39
















          What are UpValues and DownValues? The definition in the doc seems recursive: UpValue "gives a list of transformation rules corresponding to all upvalues defined for the symbol f. "
          – R zu
          Nov 22 at 19:29





          What are UpValues and DownValues? The definition in the doc seems recursive: UpValue "gives a list of transformation rules corresponding to all upvalues defined for the symbol f. "
          – R zu
          Nov 22 at 19:29













          @Rzu Maybe you can check out the documentation for UpSetDelayed and TagSetDelayed.
          – Carl Woll
          Nov 22 at 19:39





          @Rzu Maybe you can check out the documentation for UpSetDelayed and TagSetDelayed.
          – Carl Woll
          Nov 22 at 19:39


















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