A ∆ with sides 3,6,8cm. Now, a man runs around ∆ in such way that he is always at distance of 1cm from...











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I don't know to proceed in this question , I am not getting what will be the man's path . How to think about that path ?










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    A very little man, indeed.
    – ajotatxe
    Nov 19 at 18:11















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I don't know to proceed in this question , I am not getting what will be the man's path . How to think about that path ?










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  • 1




    A very little man, indeed.
    – ajotatxe
    Nov 19 at 18:11













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I don't know to proceed in this question , I am not getting what will be the man's path . How to think about that path ?










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I don't know to proceed in this question , I am not getting what will be the man's path . How to think about that path ?







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asked Nov 19 at 18:08









user580093

10816




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  • 1




    A very little man, indeed.
    – ajotatxe
    Nov 19 at 18:11














  • 1




    A very little man, indeed.
    – ajotatxe
    Nov 19 at 18:11








1




1




A very little man, indeed.
– ajotatxe
Nov 19 at 18:11




A very little man, indeed.
– ajotatxe
Nov 19 at 18:11










2 Answers
2






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2
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Hint: As he runs along each side of the triangle, the path will be parallel to the side, and exactly as long as that side. As he rounds each corner, the path will be a circular arc of radius $1$ connecting the straight components. There will be three such circular components, and they will fit together exactly to form a circle of radius $1$ (draw a picture).






share|cite|improve this answer





















  • Yeah , thanks I got it.
    – user580093
    Nov 19 at 18:20










  • So this suggests a more general result: An $epsilon$-distant path around a convex polygon of perimeter $P$ has length $P+2piepsilon$.
    – MPW
    Nov 19 at 18:22










  • is it a standard result or have some proof
    – user580093
    Nov 19 at 18:24












  • I am having difficulty in finding the length of arc , can you help me in that. finding θ in this will be very long and difficult
    – user580093
    Nov 19 at 18:27










  • It's just what you can easily observe. It should be clear that the part parallel to the sides is of the same length (the original perimeter), and that you "hook up" the sides with circular arcs of fixed radius. The only thing is to recognize that the total external angle traversed is always $360^{circ}$. That's probably a standard result.
    – MPW
    Nov 19 at 18:27




















up vote
2
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Clearly the man will be running parallel to the triangle's sides. The only problem arises in how he turns the corners. Here, he must stay 1cm from the vertex, so he'll turn the corners in circular arcs.






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    2 Answers
    2






    active

    oldest

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    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    2
    down vote



    accepted










    Hint: As he runs along each side of the triangle, the path will be parallel to the side, and exactly as long as that side. As he rounds each corner, the path will be a circular arc of radius $1$ connecting the straight components. There will be three such circular components, and they will fit together exactly to form a circle of radius $1$ (draw a picture).






    share|cite|improve this answer





















    • Yeah , thanks I got it.
      – user580093
      Nov 19 at 18:20










    • So this suggests a more general result: An $epsilon$-distant path around a convex polygon of perimeter $P$ has length $P+2piepsilon$.
      – MPW
      Nov 19 at 18:22










    • is it a standard result or have some proof
      – user580093
      Nov 19 at 18:24












    • I am having difficulty in finding the length of arc , can you help me in that. finding θ in this will be very long and difficult
      – user580093
      Nov 19 at 18:27










    • It's just what you can easily observe. It should be clear that the part parallel to the sides is of the same length (the original perimeter), and that you "hook up" the sides with circular arcs of fixed radius. The only thing is to recognize that the total external angle traversed is always $360^{circ}$. That's probably a standard result.
      – MPW
      Nov 19 at 18:27

















    up vote
    2
    down vote



    accepted










    Hint: As he runs along each side of the triangle, the path will be parallel to the side, and exactly as long as that side. As he rounds each corner, the path will be a circular arc of radius $1$ connecting the straight components. There will be three such circular components, and they will fit together exactly to form a circle of radius $1$ (draw a picture).






    share|cite|improve this answer





















    • Yeah , thanks I got it.
      – user580093
      Nov 19 at 18:20










    • So this suggests a more general result: An $epsilon$-distant path around a convex polygon of perimeter $P$ has length $P+2piepsilon$.
      – MPW
      Nov 19 at 18:22










    • is it a standard result or have some proof
      – user580093
      Nov 19 at 18:24












    • I am having difficulty in finding the length of arc , can you help me in that. finding θ in this will be very long and difficult
      – user580093
      Nov 19 at 18:27










    • It's just what you can easily observe. It should be clear that the part parallel to the sides is of the same length (the original perimeter), and that you "hook up" the sides with circular arcs of fixed radius. The only thing is to recognize that the total external angle traversed is always $360^{circ}$. That's probably a standard result.
      – MPW
      Nov 19 at 18:27















    up vote
    2
    down vote



    accepted







    up vote
    2
    down vote



    accepted






    Hint: As he runs along each side of the triangle, the path will be parallel to the side, and exactly as long as that side. As he rounds each corner, the path will be a circular arc of radius $1$ connecting the straight components. There will be three such circular components, and they will fit together exactly to form a circle of radius $1$ (draw a picture).






    share|cite|improve this answer












    Hint: As he runs along each side of the triangle, the path will be parallel to the side, and exactly as long as that side. As he rounds each corner, the path will be a circular arc of radius $1$ connecting the straight components. There will be three such circular components, and they will fit together exactly to form a circle of radius $1$ (draw a picture).







    share|cite|improve this answer












    share|cite|improve this answer



    share|cite|improve this answer










    answered Nov 19 at 18:16









    MPW

    29.7k11956




    29.7k11956












    • Yeah , thanks I got it.
      – user580093
      Nov 19 at 18:20










    • So this suggests a more general result: An $epsilon$-distant path around a convex polygon of perimeter $P$ has length $P+2piepsilon$.
      – MPW
      Nov 19 at 18:22










    • is it a standard result or have some proof
      – user580093
      Nov 19 at 18:24












    • I am having difficulty in finding the length of arc , can you help me in that. finding θ in this will be very long and difficult
      – user580093
      Nov 19 at 18:27










    • It's just what you can easily observe. It should be clear that the part parallel to the sides is of the same length (the original perimeter), and that you "hook up" the sides with circular arcs of fixed radius. The only thing is to recognize that the total external angle traversed is always $360^{circ}$. That's probably a standard result.
      – MPW
      Nov 19 at 18:27




















    • Yeah , thanks I got it.
      – user580093
      Nov 19 at 18:20










    • So this suggests a more general result: An $epsilon$-distant path around a convex polygon of perimeter $P$ has length $P+2piepsilon$.
      – MPW
      Nov 19 at 18:22










    • is it a standard result or have some proof
      – user580093
      Nov 19 at 18:24












    • I am having difficulty in finding the length of arc , can you help me in that. finding θ in this will be very long and difficult
      – user580093
      Nov 19 at 18:27










    • It's just what you can easily observe. It should be clear that the part parallel to the sides is of the same length (the original perimeter), and that you "hook up" the sides with circular arcs of fixed radius. The only thing is to recognize that the total external angle traversed is always $360^{circ}$. That's probably a standard result.
      – MPW
      Nov 19 at 18:27


















    Yeah , thanks I got it.
    – user580093
    Nov 19 at 18:20




    Yeah , thanks I got it.
    – user580093
    Nov 19 at 18:20












    So this suggests a more general result: An $epsilon$-distant path around a convex polygon of perimeter $P$ has length $P+2piepsilon$.
    – MPW
    Nov 19 at 18:22




    So this suggests a more general result: An $epsilon$-distant path around a convex polygon of perimeter $P$ has length $P+2piepsilon$.
    – MPW
    Nov 19 at 18:22












    is it a standard result or have some proof
    – user580093
    Nov 19 at 18:24






    is it a standard result or have some proof
    – user580093
    Nov 19 at 18:24














    I am having difficulty in finding the length of arc , can you help me in that. finding θ in this will be very long and difficult
    – user580093
    Nov 19 at 18:27




    I am having difficulty in finding the length of arc , can you help me in that. finding θ in this will be very long and difficult
    – user580093
    Nov 19 at 18:27












    It's just what you can easily observe. It should be clear that the part parallel to the sides is of the same length (the original perimeter), and that you "hook up" the sides with circular arcs of fixed radius. The only thing is to recognize that the total external angle traversed is always $360^{circ}$. That's probably a standard result.
    – MPW
    Nov 19 at 18:27






    It's just what you can easily observe. It should be clear that the part parallel to the sides is of the same length (the original perimeter), and that you "hook up" the sides with circular arcs of fixed radius. The only thing is to recognize that the total external angle traversed is always $360^{circ}$. That's probably a standard result.
    – MPW
    Nov 19 at 18:27












    up vote
    2
    down vote













    Clearly the man will be running parallel to the triangle's sides. The only problem arises in how he turns the corners. Here, he must stay 1cm from the vertex, so he'll turn the corners in circular arcs.






    share|cite|improve this answer

























      up vote
      2
      down vote













      Clearly the man will be running parallel to the triangle's sides. The only problem arises in how he turns the corners. Here, he must stay 1cm from the vertex, so he'll turn the corners in circular arcs.






      share|cite|improve this answer























        up vote
        2
        down vote










        up vote
        2
        down vote









        Clearly the man will be running parallel to the triangle's sides. The only problem arises in how he turns the corners. Here, he must stay 1cm from the vertex, so he'll turn the corners in circular arcs.






        share|cite|improve this answer












        Clearly the man will be running parallel to the triangle's sides. The only problem arises in how he turns the corners. Here, he must stay 1cm from the vertex, so he'll turn the corners in circular arcs.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Nov 19 at 18:12









        Y. Forman

        11.4k423




        11.4k423






























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