Partial derivatives of the dependent variable.












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I have a function of the form $$f(x,y)=frac{1}{exp((y-mu)/tau)+1 }$$ where $mu,tau,m$ are constants. Also $y^2=x^2+m^2$. How do I calculate $frac{partial f}{partial x}$ and $frac{partial f}{partial y}$. Can I just not substitute the value of y in the expression?










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  • $begingroup$
    Are you sure that the question is complete? Since it seems that $f$ is a function of $y$ only and so we just have to replace $partial$ by $text{d}$.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:02












  • $begingroup$
    I am sure that this is the question. btw, are you trying to tell me that $frac{partial f}{partial x}=0$ for the given expression? Why cannot I substitute the expression of y(x) here?
    $endgroup$
    – Icchyamoy
    Dec 29 '18 at 10:05










  • $begingroup$
    I mean that the partial derivative is the same as the regular one. And yes, you can definitely substitute.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:06
















0












$begingroup$


I have a function of the form $$f(x,y)=frac{1}{exp((y-mu)/tau)+1 }$$ where $mu,tau,m$ are constants. Also $y^2=x^2+m^2$. How do I calculate $frac{partial f}{partial x}$ and $frac{partial f}{partial y}$. Can I just not substitute the value of y in the expression?










share|cite|improve this question











$endgroup$












  • $begingroup$
    Are you sure that the question is complete? Since it seems that $f$ is a function of $y$ only and so we just have to replace $partial$ by $text{d}$.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:02












  • $begingroup$
    I am sure that this is the question. btw, are you trying to tell me that $frac{partial f}{partial x}=0$ for the given expression? Why cannot I substitute the expression of y(x) here?
    $endgroup$
    – Icchyamoy
    Dec 29 '18 at 10:05










  • $begingroup$
    I mean that the partial derivative is the same as the regular one. And yes, you can definitely substitute.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:06














0












0








0





$begingroup$


I have a function of the form $$f(x,y)=frac{1}{exp((y-mu)/tau)+1 }$$ where $mu,tau,m$ are constants. Also $y^2=x^2+m^2$. How do I calculate $frac{partial f}{partial x}$ and $frac{partial f}{partial y}$. Can I just not substitute the value of y in the expression?










share|cite|improve this question











$endgroup$




I have a function of the form $$f(x,y)=frac{1}{exp((y-mu)/tau)+1 }$$ where $mu,tau,m$ are constants. Also $y^2=x^2+m^2$. How do I calculate $frac{partial f}{partial x}$ and $frac{partial f}{partial y}$. Can I just not substitute the value of y in the expression?







multivariable-calculus partial-derivative






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edited Dec 29 '18 at 10:55









Atheesh Rathnaweera

31




31










asked Dec 29 '18 at 9:51









IcchyamoyIcchyamoy

11




11












  • $begingroup$
    Are you sure that the question is complete? Since it seems that $f$ is a function of $y$ only and so we just have to replace $partial$ by $text{d}$.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:02












  • $begingroup$
    I am sure that this is the question. btw, are you trying to tell me that $frac{partial f}{partial x}=0$ for the given expression? Why cannot I substitute the expression of y(x) here?
    $endgroup$
    – Icchyamoy
    Dec 29 '18 at 10:05










  • $begingroup$
    I mean that the partial derivative is the same as the regular one. And yes, you can definitely substitute.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:06


















  • $begingroup$
    Are you sure that the question is complete? Since it seems that $f$ is a function of $y$ only and so we just have to replace $partial$ by $text{d}$.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:02












  • $begingroup$
    I am sure that this is the question. btw, are you trying to tell me that $frac{partial f}{partial x}=0$ for the given expression? Why cannot I substitute the expression of y(x) here?
    $endgroup$
    – Icchyamoy
    Dec 29 '18 at 10:05










  • $begingroup$
    I mean that the partial derivative is the same as the regular one. And yes, you can definitely substitute.
    $endgroup$
    – Devashish Kaushik
    Dec 29 '18 at 10:06
















$begingroup$
Are you sure that the question is complete? Since it seems that $f$ is a function of $y$ only and so we just have to replace $partial$ by $text{d}$.
$endgroup$
– Devashish Kaushik
Dec 29 '18 at 10:02






$begingroup$
Are you sure that the question is complete? Since it seems that $f$ is a function of $y$ only and so we just have to replace $partial$ by $text{d}$.
$endgroup$
– Devashish Kaushik
Dec 29 '18 at 10:02














$begingroup$
I am sure that this is the question. btw, are you trying to tell me that $frac{partial f}{partial x}=0$ for the given expression? Why cannot I substitute the expression of y(x) here?
$endgroup$
– Icchyamoy
Dec 29 '18 at 10:05




$begingroup$
I am sure that this is the question. btw, are you trying to tell me that $frac{partial f}{partial x}=0$ for the given expression? Why cannot I substitute the expression of y(x) here?
$endgroup$
– Icchyamoy
Dec 29 '18 at 10:05












$begingroup$
I mean that the partial derivative is the same as the regular one. And yes, you can definitely substitute.
$endgroup$
– Devashish Kaushik
Dec 29 '18 at 10:06




$begingroup$
I mean that the partial derivative is the same as the regular one. And yes, you can definitely substitute.
$endgroup$
– Devashish Kaushik
Dec 29 '18 at 10:06










1 Answer
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$begingroup$

If $mu$, $tau$,and $m$ are really constants, then $f$ is purely a function of $y$, i.e.



$$f(x,y)=f(y)=frac{1}{exp((y-mu)/tau)+1 }= frac{1}{exp((sqrt{x^2 + m^2} - mu ) / tau ) -1}$$



The partial derivatives are then just the regular derivatives, so you just differentiate as you would normally.






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    1 Answer
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    $begingroup$

    If $mu$, $tau$,and $m$ are really constants, then $f$ is purely a function of $y$, i.e.



    $$f(x,y)=f(y)=frac{1}{exp((y-mu)/tau)+1 }= frac{1}{exp((sqrt{x^2 + m^2} - mu ) / tau ) -1}$$



    The partial derivatives are then just the regular derivatives, so you just differentiate as you would normally.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      If $mu$, $tau$,and $m$ are really constants, then $f$ is purely a function of $y$, i.e.



      $$f(x,y)=f(y)=frac{1}{exp((y-mu)/tau)+1 }= frac{1}{exp((sqrt{x^2 + m^2} - mu ) / tau ) -1}$$



      The partial derivatives are then just the regular derivatives, so you just differentiate as you would normally.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        If $mu$, $tau$,and $m$ are really constants, then $f$ is purely a function of $y$, i.e.



        $$f(x,y)=f(y)=frac{1}{exp((y-mu)/tau)+1 }= frac{1}{exp((sqrt{x^2 + m^2} - mu ) / tau ) -1}$$



        The partial derivatives are then just the regular derivatives, so you just differentiate as you would normally.






        share|cite|improve this answer









        $endgroup$



        If $mu$, $tau$,and $m$ are really constants, then $f$ is purely a function of $y$, i.e.



        $$f(x,y)=f(y)=frac{1}{exp((y-mu)/tau)+1 }= frac{1}{exp((sqrt{x^2 + m^2} - mu ) / tau ) -1}$$



        The partial derivatives are then just the regular derivatives, so you just differentiate as you would normally.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 29 '18 at 10:11









        Devashish KaushikDevashish Kaushik

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