Limit of a continuous angle












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Let $gamma :[0,1] to mathbb{R}^2$ be an injective continuous map. Consider point $P$ in $mathbb{R}^2$ outside of the curve $gamma$ and $A,B$ be the two ending points $gamma(0)$, $gamma(1)$ of the curve respectly. We fix point $M$ on the curve somewhere between $A$ and $B$. Now point $C$ on the curve moves continuously from $A$ to $B$ crossing $M$.



What can we say about both left and right limits of $lim_{C to M} angle PCM$ ? (the angle is signed with respect to clockwork orienration).










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  • $begingroup$
    I would guess they represent the angle at which the line segment PM crosses the image of $gamma$.
    $endgroup$
    – Stan Tendijck
    Jan 27 at 0:28
















1












$begingroup$


Let $gamma :[0,1] to mathbb{R}^2$ be an injective continuous map. Consider point $P$ in $mathbb{R}^2$ outside of the curve $gamma$ and $A,B$ be the two ending points $gamma(0)$, $gamma(1)$ of the curve respectly. We fix point $M$ on the curve somewhere between $A$ and $B$. Now point $C$ on the curve moves continuously from $A$ to $B$ crossing $M$.



What can we say about both left and right limits of $lim_{C to M} angle PCM$ ? (the angle is signed with respect to clockwork orienration).










share|cite|improve this question











$endgroup$












  • $begingroup$
    I would guess they represent the angle at which the line segment PM crosses the image of $gamma$.
    $endgroup$
    – Stan Tendijck
    Jan 27 at 0:28














1












1








1





$begingroup$


Let $gamma :[0,1] to mathbb{R}^2$ be an injective continuous map. Consider point $P$ in $mathbb{R}^2$ outside of the curve $gamma$ and $A,B$ be the two ending points $gamma(0)$, $gamma(1)$ of the curve respectly. We fix point $M$ on the curve somewhere between $A$ and $B$. Now point $C$ on the curve moves continuously from $A$ to $B$ crossing $M$.



What can we say about both left and right limits of $lim_{C to M} angle PCM$ ? (the angle is signed with respect to clockwork orienration).










share|cite|improve this question











$endgroup$




Let $gamma :[0,1] to mathbb{R}^2$ be an injective continuous map. Consider point $P$ in $mathbb{R}^2$ outside of the curve $gamma$ and $A,B$ be the two ending points $gamma(0)$, $gamma(1)$ of the curve respectly. We fix point $M$ on the curve somewhere between $A$ and $B$. Now point $C$ on the curve moves continuously from $A$ to $B$ crossing $M$.



What can we say about both left and right limits of $lim_{C to M} angle PCM$ ? (the angle is signed with respect to clockwork orienration).







geometry limits






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edited Jan 27 at 0:11









Bungo

13.7k22148




13.7k22148










asked Jan 27 at 0:09









MasMMasM

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11611












  • $begingroup$
    I would guess they represent the angle at which the line segment PM crosses the image of $gamma$.
    $endgroup$
    – Stan Tendijck
    Jan 27 at 0:28


















  • $begingroup$
    I would guess they represent the angle at which the line segment PM crosses the image of $gamma$.
    $endgroup$
    – Stan Tendijck
    Jan 27 at 0:28
















$begingroup$
I would guess they represent the angle at which the line segment PM crosses the image of $gamma$.
$endgroup$
– Stan Tendijck
Jan 27 at 0:28




$begingroup$
I would guess they represent the angle at which the line segment PM crosses the image of $gamma$.
$endgroup$
– Stan Tendijck
Jan 27 at 0:28










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Line $CM$, as $Cto M$, tends to the line tangent at $M$ to the curve (provided that tangent exists, i.e. if $gamma$ is differentiable). Hence $angle PCM$ tends to the angle between line $PM$ and the tangent at $M$. Of course left and right limit give the two (different) angles formed by such lines.






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    $begingroup$

    Line $CM$, as $Cto M$, tends to the line tangent at $M$ to the curve (provided that tangent exists, i.e. if $gamma$ is differentiable). Hence $angle PCM$ tends to the angle between line $PM$ and the tangent at $M$. Of course left and right limit give the two (different) angles formed by such lines.






    share|cite|improve this answer











    $endgroup$


















      1












      $begingroup$

      Line $CM$, as $Cto M$, tends to the line tangent at $M$ to the curve (provided that tangent exists, i.e. if $gamma$ is differentiable). Hence $angle PCM$ tends to the angle between line $PM$ and the tangent at $M$. Of course left and right limit give the two (different) angles formed by such lines.






      share|cite|improve this answer











      $endgroup$
















        1












        1








        1





        $begingroup$

        Line $CM$, as $Cto M$, tends to the line tangent at $M$ to the curve (provided that tangent exists, i.e. if $gamma$ is differentiable). Hence $angle PCM$ tends to the angle between line $PM$ and the tangent at $M$. Of course left and right limit give the two (different) angles formed by such lines.






        share|cite|improve this answer











        $endgroup$



        Line $CM$, as $Cto M$, tends to the line tangent at $M$ to the curve (provided that tangent exists, i.e. if $gamma$ is differentiable). Hence $angle PCM$ tends to the angle between line $PM$ and the tangent at $M$. Of course left and right limit give the two (different) angles formed by such lines.







        share|cite|improve this answer














        share|cite|improve this answer



        share|cite|improve this answer








        edited Jan 28 at 11:38

























        answered Jan 27 at 9:24









        AretinoAretino

        25.5k21445




        25.5k21445






























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