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












1














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 '18 at 14:50
















1














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 '18 at 14:50














1












1








1







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 '18 at 14:12









Mango164

484




484












  • Spanning, yes, but not minimally spanning
    – MPW
    Dec 2 '18 at 14:50


















  • Spanning, yes, but not minimally spanning
    – MPW
    Dec 2 '18 at 14:50
















Spanning, yes, but not minimally spanning
– MPW
Dec 2 '18 at 14:50




Spanning, yes, but not minimally spanning
– MPW
Dec 2 '18 at 14:50










2 Answers
2






active

oldest

votes


















1














${0,0,1),(0,0,2)}$ 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 '18 at 14:18






  • 1




    yes, it is possible.
    – Siong Thye Goh
    Dec 2 '18 at 14:23



















1














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









    1














    ${0,0,1),(0,0,2)}$ 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 '18 at 14:18






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 '18 at 14:23
















    1














    ${0,0,1),(0,0,2)}$ 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 '18 at 14:18






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 '18 at 14:23














    1












    1








    1






    ${0,0,1),(0,0,2)}$ 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 '18 at 14:15









    Siong Thye Goh

    99.5k1465117




    99.5k1465117












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






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 '18 at 14:23


















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






    • 1




      yes, it is possible.
      – Siong Thye Goh
      Dec 2 '18 at 14:23
















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




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




    1




    1




    yes, it is possible.
    – Siong Thye Goh
    Dec 2 '18 at 14:23




    yes, it is possible.
    – Siong Thye Goh
    Dec 2 '18 at 14:23











    1














    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


























      1














      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
























        1












        1








        1






        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 '18 at 14:15









        greedoid

        38.1k114795




        38.1k114795






























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