Find the orthogonal trajectory to the family of curves $x^2+y^2=4c^2$ where $c$ is a constant.












-1












$begingroup$


Differentiate w.r.t $x$:



$$x+yfrac{dx}{dy}=4c^2$$










share|cite|improve this question











$endgroup$












  • $begingroup$
    Your differentiation is wrong. The derivative of a constant is 0 and you want $frac{dy}{dx}$, not $frac{dx}{dy}$. You should have $x+ yfrac{dy}{dx}= 0$. From that $frac{dy}{dx}= -frac{x}{y}$ and the orthogonal complement will satisfy $frac{dy}{dx}= frac{y}{x}$.
    $endgroup$
    – user247327
    Dec 6 '18 at 12:33










  • $begingroup$
    I would argue the derivative w.r.t $x$ equals $2x + y frac{delta y}{delta x} = 0$, thus $frac{delta y}{delta x}=frac{-2x}{y}$. Hope this helps.
    $endgroup$
    – Mathbeginner
    Dec 6 '18 at 12:44


















-1












$begingroup$


Differentiate w.r.t $x$:



$$x+yfrac{dx}{dy}=4c^2$$










share|cite|improve this question











$endgroup$












  • $begingroup$
    Your differentiation is wrong. The derivative of a constant is 0 and you want $frac{dy}{dx}$, not $frac{dx}{dy}$. You should have $x+ yfrac{dy}{dx}= 0$. From that $frac{dy}{dx}= -frac{x}{y}$ and the orthogonal complement will satisfy $frac{dy}{dx}= frac{y}{x}$.
    $endgroup$
    – user247327
    Dec 6 '18 at 12:33










  • $begingroup$
    I would argue the derivative w.r.t $x$ equals $2x + y frac{delta y}{delta x} = 0$, thus $frac{delta y}{delta x}=frac{-2x}{y}$. Hope this helps.
    $endgroup$
    – Mathbeginner
    Dec 6 '18 at 12:44
















-1












-1








-1





$begingroup$


Differentiate w.r.t $x$:



$$x+yfrac{dx}{dy}=4c^2$$










share|cite|improve this question











$endgroup$




Differentiate w.r.t $x$:



$$x+yfrac{dx}{dy}=4c^2$$







hyperbolic-functions






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 6 '18 at 12:39









amWhy

1




1










asked Dec 6 '18 at 12:14









Best 4 YouBest 4 You

1




1












  • $begingroup$
    Your differentiation is wrong. The derivative of a constant is 0 and you want $frac{dy}{dx}$, not $frac{dx}{dy}$. You should have $x+ yfrac{dy}{dx}= 0$. From that $frac{dy}{dx}= -frac{x}{y}$ and the orthogonal complement will satisfy $frac{dy}{dx}= frac{y}{x}$.
    $endgroup$
    – user247327
    Dec 6 '18 at 12:33










  • $begingroup$
    I would argue the derivative w.r.t $x$ equals $2x + y frac{delta y}{delta x} = 0$, thus $frac{delta y}{delta x}=frac{-2x}{y}$. Hope this helps.
    $endgroup$
    – Mathbeginner
    Dec 6 '18 at 12:44




















  • $begingroup$
    Your differentiation is wrong. The derivative of a constant is 0 and you want $frac{dy}{dx}$, not $frac{dx}{dy}$. You should have $x+ yfrac{dy}{dx}= 0$. From that $frac{dy}{dx}= -frac{x}{y}$ and the orthogonal complement will satisfy $frac{dy}{dx}= frac{y}{x}$.
    $endgroup$
    – user247327
    Dec 6 '18 at 12:33










  • $begingroup$
    I would argue the derivative w.r.t $x$ equals $2x + y frac{delta y}{delta x} = 0$, thus $frac{delta y}{delta x}=frac{-2x}{y}$. Hope this helps.
    $endgroup$
    – Mathbeginner
    Dec 6 '18 at 12:44


















$begingroup$
Your differentiation is wrong. The derivative of a constant is 0 and you want $frac{dy}{dx}$, not $frac{dx}{dy}$. You should have $x+ yfrac{dy}{dx}= 0$. From that $frac{dy}{dx}= -frac{x}{y}$ and the orthogonal complement will satisfy $frac{dy}{dx}= frac{y}{x}$.
$endgroup$
– user247327
Dec 6 '18 at 12:33




$begingroup$
Your differentiation is wrong. The derivative of a constant is 0 and you want $frac{dy}{dx}$, not $frac{dx}{dy}$. You should have $x+ yfrac{dy}{dx}= 0$. From that $frac{dy}{dx}= -frac{x}{y}$ and the orthogonal complement will satisfy $frac{dy}{dx}= frac{y}{x}$.
$endgroup$
– user247327
Dec 6 '18 at 12:33












$begingroup$
I would argue the derivative w.r.t $x$ equals $2x + y frac{delta y}{delta x} = 0$, thus $frac{delta y}{delta x}=frac{-2x}{y}$. Hope this helps.
$endgroup$
– Mathbeginner
Dec 6 '18 at 12:44






$begingroup$
I would argue the derivative w.r.t $x$ equals $2x + y frac{delta y}{delta x} = 0$, thus $frac{delta y}{delta x}=frac{-2x}{y}$. Hope this helps.
$endgroup$
– Mathbeginner
Dec 6 '18 at 12:44












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$begingroup$

$$x+yy'=0$$ turns to



$$x-frac y{y'}=0$$ which integrates as $$y=cx.$$



This was expected as the given family is made of circles centered at the origin.






share|cite|improve this answer









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    1 Answer
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    active

    oldest

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    1 Answer
    1






    active

    oldest

    votes









    active

    oldest

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    active

    oldest

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    0












    $begingroup$

    $$x+yy'=0$$ turns to



    $$x-frac y{y'}=0$$ which integrates as $$y=cx.$$



    This was expected as the given family is made of circles centered at the origin.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      $$x+yy'=0$$ turns to



      $$x-frac y{y'}=0$$ which integrates as $$y=cx.$$



      This was expected as the given family is made of circles centered at the origin.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        $$x+yy'=0$$ turns to



        $$x-frac y{y'}=0$$ which integrates as $$y=cx.$$



        This was expected as the given family is made of circles centered at the origin.






        share|cite|improve this answer









        $endgroup$



        $$x+yy'=0$$ turns to



        $$x-frac y{y'}=0$$ which integrates as $$y=cx.$$



        This was expected as the given family is made of circles centered at the origin.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 6 '18 at 12:48









        Yves DaoustYves Daoust

        126k672226




        126k672226






























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