Why isn't a linearly dependent set in $mathbb R^n$ a spanning set in $mathbb R^n$?











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Aren't there some cases where they do in fact span $mathbb R^n$?



E.g: the set of vectors $(1, 0, 0), (0, 1, 0), (0,0,1), (0,0,2)$ in $mathbb R^3$



Clearly the first three vectors form a basis for $mathbb R^3$ and span all of $mathbb R^3$. The vector $(0,0,2)$ can also be used in different scalar combinations with other vectors in the set to reach any point $mathbb R^3$ so why would adding it to the set suddenly make the set not span $mathbb R^3$?



Might it be due to some formal definition of a spanning set of a subspace being the basis of that subspace or something alike?










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  • Spanning, yes, but not minimally spanning
    – MPW
    Dec 2 at 14:50















up vote
1
down vote

favorite












Aren't there some cases where they do in fact span $mathbb R^n$?



E.g: the set of vectors $(1, 0, 0), (0, 1, 0), (0,0,1), (0,0,2)$ in $mathbb R^3$



Clearly the first three vectors form a basis for $mathbb R^3$ and span all of $mathbb R^3$. The vector $(0,0,2)$ can also be used in different scalar combinations with other vectors in the set to reach any point $mathbb R^3$ so why would adding it to the set suddenly make the set not span $mathbb R^3$?



Might it be due to some formal definition of a spanning set of a subspace being the basis of that subspace or something alike?










share|cite|improve this question






















  • Spanning, yes, but not minimally spanning
    – MPW
    Dec 2 at 14:50













up vote
1
down vote

favorite









up vote
1
down vote

favorite











Aren't there some cases where they do in fact span $mathbb R^n$?



E.g: the set of vectors $(1, 0, 0), (0, 1, 0), (0,0,1), (0,0,2)$ in $mathbb R^3$



Clearly the first three vectors form a basis for $mathbb R^3$ and span all of $mathbb R^3$. The vector $(0,0,2)$ can also be used in different scalar combinations with other vectors in the set to reach any point $mathbb R^3$ so why would adding it to the set suddenly make the set not span $mathbb R^3$?



Might it be due to some formal definition of a spanning set of a subspace being the basis of that subspace or something alike?










share|cite|improve this question













Aren't there some cases where they do in fact span $mathbb R^n$?



E.g: the set of vectors $(1, 0, 0), (0, 1, 0), (0,0,1), (0,0,2)$ in $mathbb R^3$



Clearly the first three vectors form a basis for $mathbb R^3$ and span all of $mathbb R^3$. The vector $(0,0,2)$ can also be used in different scalar combinations with other vectors in the set to reach any point $mathbb R^3$ so why would adding it to the set suddenly make the set not span $mathbb R^3$?



Might it be due to some formal definition of a spanning set of a subspace being the basis of that subspace or something alike?







linear-algebra






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asked Dec 2 at 14:12









Mango164

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  • Spanning, yes, but not minimally spanning
    – MPW
    Dec 2 at 14:50


















  • Spanning, yes, but not minimally spanning
    – MPW
    Dec 2 at 14:50
















Spanning, yes, but not minimally spanning
– MPW
Dec 2 at 14:50




Spanning, yes, but not minimally spanning
– MPW
Dec 2 at 14:50










2 Answers
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up vote
1
down vote



accepted










${0,0,1),(0,0,2)}$ is not linearly independent and they do not span $mathbb{R}^3$.



If you already have a set that span $mathbb{R}^n$, adding more vectors do not change the property that it span $mathbb{R}^n$.






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  • Therefore a linearly dependent set can in fact span $mathbb R^3$?
    – Mango164
    Dec 2 at 14:18






  • 1




    yes, it is possible.
    – Siong Thye Goh
    Dec 2 at 14:23


















up vote
1
down vote













That set of vectors does span $mathbb{R}^3$ but it is not linear independent.



So if some set is not linear independant it can still span some space.



If you add any vector to base set of space $V$ it still spans $V$.






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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes








    up vote
    1
    down vote



    accepted










    ${0,0,1),(0,0,2)}$ is not linearly independent and they do not span $mathbb{R}^3$.



    If you already have a set that span $mathbb{R}^n$, adding more vectors do not change the property that it span $mathbb{R}^n$.






    share|cite|improve this answer





















    • Therefore a linearly dependent set can in fact span $mathbb R^3$?
      – Mango164
      Dec 2 at 14:18






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 at 14:23















    up vote
    1
    down vote



    accepted










    ${0,0,1),(0,0,2)}$ is not linearly independent and they do not span $mathbb{R}^3$.



    If you already have a set that span $mathbb{R}^n$, adding more vectors do not change the property that it span $mathbb{R}^n$.






    share|cite|improve this answer





















    • Therefore a linearly dependent set can in fact span $mathbb R^3$?
      – Mango164
      Dec 2 at 14:18






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 at 14:23













    up vote
    1
    down vote



    accepted







    up vote
    1
    down vote



    accepted






    ${0,0,1),(0,0,2)}$ is not linearly independent and they do not span $mathbb{R}^3$.



    If you already have a set that span $mathbb{R}^n$, adding more vectors do not change the property that it span $mathbb{R}^n$.






    share|cite|improve this answer












    ${0,0,1),(0,0,2)}$ is not linearly independent and they do not span $mathbb{R}^3$.



    If you already have a set that span $mathbb{R}^n$, adding more vectors do not change the property that it span $mathbb{R}^n$.







    share|cite|improve this answer












    share|cite|improve this answer



    share|cite|improve this answer










    answered Dec 2 at 14:15









    Siong Thye Goh

    96.4k1462116




    96.4k1462116












    • Therefore a linearly dependent set can in fact span $mathbb R^3$?
      – Mango164
      Dec 2 at 14:18






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 at 14:23


















    • Therefore a linearly dependent set can in fact span $mathbb R^3$?
      – Mango164
      Dec 2 at 14:18






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 at 14:23
















    Therefore a linearly dependent set can in fact span $mathbb R^3$?
    – Mango164
    Dec 2 at 14:18




    Therefore a linearly dependent set can in fact span $mathbb R^3$?
    – Mango164
    Dec 2 at 14:18




    1




    1




    yes, it is possible.
    – Siong Thye Goh
    Dec 2 at 14:23




    yes, it is possible.
    – Siong Thye Goh
    Dec 2 at 14:23










    up vote
    1
    down vote













    That set of vectors does span $mathbb{R}^3$ but it is not linear independent.



    So if some set is not linear independant it can still span some space.



    If you add any vector to base set of space $V$ it still spans $V$.






    share|cite|improve this answer

























      up vote
      1
      down vote













      That set of vectors does span $mathbb{R}^3$ but it is not linear independent.



      So if some set is not linear independant it can still span some space.



      If you add any vector to base set of space $V$ it still spans $V$.






      share|cite|improve this answer























        up vote
        1
        down vote










        up vote
        1
        down vote









        That set of vectors does span $mathbb{R}^3$ but it is not linear independent.



        So if some set is not linear independant it can still span some space.



        If you add any vector to base set of space $V$ it still spans $V$.






        share|cite|improve this answer












        That set of vectors does span $mathbb{R}^3$ but it is not linear independent.



        So if some set is not linear independant it can still span some space.



        If you add any vector to base set of space $V$ it still spans $V$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 2 at 14:15









        greedoid

        36.1k114591




        36.1k114591






























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