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How can I visualize $cmathbfv + (1 - c)mathbfw$?


Geometric/Visual Solution - Shortest Vector for which Dot Product = x + 2y = 5. (Strang P21 1.2.26)Row and Column Picture of a 3 x 3 Singular Matrix (Strang P43, 2.1.32)Column and Row Picture for Singular System of 100 Equations (Strang P55, 2.2.32)Columns of A - Linear independence, span, rank. [GStrang P180, 3.5.19]Do the vectors not in the column space form a subspace? [GStrang P130 3.1.27]Problem with alternate solution — Equation of plane through point and containing intersection line of two planes [Stewart P $803, 12.5.37$]How is the “two intersecting lines” picture of a system of two linear equations related to the “sum of two vectors” picture?How Can the Maximum Number of Moves Needed to Solve a 3x3x3 Rubik's Cube Be Simply ProvenFind the line through the origin farthest to the points (1,1), (1,−1), and (−1,−1).Sampling points on a plane defined by three points













5












$begingroup$



Draw the line of all combinations that has $cmathbfv + dmathbfw$ and $c + d = 1$.



Solution: All combinations with $c + d = 1$ are on the line that passes through $mathbfv$ and $mathbfw$.




enter image description hereenter image description hereenter image description here



  1. $cmathbfv + dmathbfw quad & quad c + d = 1 implies cmathbfv + (1 - c)mathbfw$.

    But how do I draw $(1 - c)mathbfw$?


  2. My $c = 1.5$ sketch fits the solution. But why doesn't my sketch for $c = -0.5$?


I additionally tried $cmathbfv + (1 - c)mathbfw = color#318CE7c(mathbfv - mathbfw) + mathbfw $ in picture 2 but it doesn't agree with solution?



  1. How can I get the solution algebraically, without pictures?









share|cite|improve this question











$endgroup$











  • $begingroup$
    I think in picture 2 if you shifted the initial point of c(v-w) to origin then your observation will agree with the result..
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:08










  • $begingroup$
    And for $c=-0.5$, start $-0.5v$ from origin...
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:16















5












$begingroup$



Draw the line of all combinations that has $cmathbfv + dmathbfw$ and $c + d = 1$.



Solution: All combinations with $c + d = 1$ are on the line that passes through $mathbfv$ and $mathbfw$.




enter image description hereenter image description hereenter image description here



  1. $cmathbfv + dmathbfw quad & quad c + d = 1 implies cmathbfv + (1 - c)mathbfw$.

    But how do I draw $(1 - c)mathbfw$?


  2. My $c = 1.5$ sketch fits the solution. But why doesn't my sketch for $c = -0.5$?


I additionally tried $cmathbfv + (1 - c)mathbfw = color#318CE7c(mathbfv - mathbfw) + mathbfw $ in picture 2 but it doesn't agree with solution?



  1. How can I get the solution algebraically, without pictures?









share|cite|improve this question











$endgroup$











  • $begingroup$
    I think in picture 2 if you shifted the initial point of c(v-w) to origin then your observation will agree with the result..
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:08










  • $begingroup$
    And for $c=-0.5$, start $-0.5v$ from origin...
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:16













5












5








5


2



$begingroup$



Draw the line of all combinations that has $cmathbfv + dmathbfw$ and $c + d = 1$.



Solution: All combinations with $c + d = 1$ are on the line that passes through $mathbfv$ and $mathbfw$.




enter image description hereenter image description hereenter image description here



  1. $cmathbfv + dmathbfw quad & quad c + d = 1 implies cmathbfv + (1 - c)mathbfw$.

    But how do I draw $(1 - c)mathbfw$?


  2. My $c = 1.5$ sketch fits the solution. But why doesn't my sketch for $c = -0.5$?


I additionally tried $cmathbfv + (1 - c)mathbfw = color#318CE7c(mathbfv - mathbfw) + mathbfw $ in picture 2 but it doesn't agree with solution?



  1. How can I get the solution algebraically, without pictures?









share|cite|improve this question











$endgroup$





Draw the line of all combinations that has $cmathbfv + dmathbfw$ and $c + d = 1$.



Solution: All combinations with $c + d = 1$ are on the line that passes through $mathbfv$ and $mathbfw$.




enter image description hereenter image description hereenter image description here



  1. $cmathbfv + dmathbfw quad & quad c + d = 1 implies cmathbfv + (1 - c)mathbfw$.

    But how do I draw $(1 - c)mathbfw$?


  2. My $c = 1.5$ sketch fits the solution. But why doesn't my sketch for $c = -0.5$?


I additionally tried $cmathbfv + (1 - c)mathbfw = color#318CE7c(mathbfv - mathbfw) + mathbfw $ in picture 2 but it doesn't agree with solution?



  1. How can I get the solution algebraically, without pictures?






linear-algebra vector-spaces






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Mar 15 at 3:43







Adopt. Don't reproduce.

















asked Jul 31 '13 at 7:52









Adopt. Don't reproduce.Adopt. Don't reproduce.

264




264











  • $begingroup$
    I think in picture 2 if you shifted the initial point of c(v-w) to origin then your observation will agree with the result..
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:08










  • $begingroup$
    And for $c=-0.5$, start $-0.5v$ from origin...
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:16
















  • $begingroup$
    I think in picture 2 if you shifted the initial point of c(v-w) to origin then your observation will agree with the result..
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:08










  • $begingroup$
    And for $c=-0.5$, start $-0.5v$ from origin...
    $endgroup$
    – Ritu
    Feb 20 '15 at 7:16















$begingroup$
I think in picture 2 if you shifted the initial point of c(v-w) to origin then your observation will agree with the result..
$endgroup$
– Ritu
Feb 20 '15 at 7:08




$begingroup$
I think in picture 2 if you shifted the initial point of c(v-w) to origin then your observation will agree with the result..
$endgroup$
– Ritu
Feb 20 '15 at 7:08












$begingroup$
And for $c=-0.5$, start $-0.5v$ from origin...
$endgroup$
– Ritu
Feb 20 '15 at 7:16




$begingroup$
And for $c=-0.5$, start $-0.5v$ from origin...
$endgroup$
– Ritu
Feb 20 '15 at 7:16










2 Answers
2






active

oldest

votes


















2












$begingroup$

Maybe this little illustration will help too (sorry for the quality). The problem in issue#2 is the wrong addition of vectors.



enter image description here






share|cite|improve this answer









$endgroup$




















    1












    $begingroup$

    Suppose $AB$ and $AC$ are your vectors $v$ and $w$, respectively. Then $AD$ is your convex combination $uv+(1-u)w$, where $uv$ is $AF$, and $AE$ is $(1-u)w$. The similarities between the triangles $BFD$, $EDC$ and $ABC$ explains it.



    The fact that $BD+DC=BC$ is related to $(1-u)+u=1$, because you get $BD/BC+DC/BC=1$. Now, the triangles similarities gives you that $BD/BC=FD/AC=AE/AC=1-u$ and $DC/BC=ED/AB=AF/AB=u$.



    enter image description here






    share|cite|improve this answer











    $endgroup$












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      2 Answers
      2






      active

      oldest

      votes








      2 Answers
      2






      active

      oldest

      votes









      active

      oldest

      votes






      active

      oldest

      votes









      2












      $begingroup$

      Maybe this little illustration will help too (sorry for the quality). The problem in issue#2 is the wrong addition of vectors.



      enter image description here






      share|cite|improve this answer









      $endgroup$

















        2












        $begingroup$

        Maybe this little illustration will help too (sorry for the quality). The problem in issue#2 is the wrong addition of vectors.



        enter image description here






        share|cite|improve this answer









        $endgroup$















          2












          2








          2





          $begingroup$

          Maybe this little illustration will help too (sorry for the quality). The problem in issue#2 is the wrong addition of vectors.



          enter image description here






          share|cite|improve this answer









          $endgroup$



          Maybe this little illustration will help too (sorry for the quality). The problem in issue#2 is the wrong addition of vectors.



          enter image description here







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Jul 31 '13 at 8:42









          EvgenyEvgeny

          4,71021022




          4,71021022





















              1












              $begingroup$

              Suppose $AB$ and $AC$ are your vectors $v$ and $w$, respectively. Then $AD$ is your convex combination $uv+(1-u)w$, where $uv$ is $AF$, and $AE$ is $(1-u)w$. The similarities between the triangles $BFD$, $EDC$ and $ABC$ explains it.



              The fact that $BD+DC=BC$ is related to $(1-u)+u=1$, because you get $BD/BC+DC/BC=1$. Now, the triangles similarities gives you that $BD/BC=FD/AC=AE/AC=1-u$ and $DC/BC=ED/AB=AF/AB=u$.



              enter image description here






              share|cite|improve this answer











              $endgroup$

















                1












                $begingroup$

                Suppose $AB$ and $AC$ are your vectors $v$ and $w$, respectively. Then $AD$ is your convex combination $uv+(1-u)w$, where $uv$ is $AF$, and $AE$ is $(1-u)w$. The similarities between the triangles $BFD$, $EDC$ and $ABC$ explains it.



                The fact that $BD+DC=BC$ is related to $(1-u)+u=1$, because you get $BD/BC+DC/BC=1$. Now, the triangles similarities gives you that $BD/BC=FD/AC=AE/AC=1-u$ and $DC/BC=ED/AB=AF/AB=u$.



                enter image description here






                share|cite|improve this answer











                $endgroup$















                  1












                  1








                  1





                  $begingroup$

                  Suppose $AB$ and $AC$ are your vectors $v$ and $w$, respectively. Then $AD$ is your convex combination $uv+(1-u)w$, where $uv$ is $AF$, and $AE$ is $(1-u)w$. The similarities between the triangles $BFD$, $EDC$ and $ABC$ explains it.



                  The fact that $BD+DC=BC$ is related to $(1-u)+u=1$, because you get $BD/BC+DC/BC=1$. Now, the triangles similarities gives you that $BD/BC=FD/AC=AE/AC=1-u$ and $DC/BC=ED/AB=AF/AB=u$.



                  enter image description here






                  share|cite|improve this answer











                  $endgroup$



                  Suppose $AB$ and $AC$ are your vectors $v$ and $w$, respectively. Then $AD$ is your convex combination $uv+(1-u)w$, where $uv$ is $AF$, and $AE$ is $(1-u)w$. The similarities between the triangles $BFD$, $EDC$ and $ABC$ explains it.



                  The fact that $BD+DC=BC$ is related to $(1-u)+u=1$, because you get $BD/BC+DC/BC=1$. Now, the triangles similarities gives you that $BD/BC=FD/AC=AE/AC=1-u$ and $DC/BC=ED/AB=AF/AB=u$.



                  enter image description here







                  share|cite|improve this answer














                  share|cite|improve this answer



                  share|cite|improve this answer








                  edited Jul 31 '13 at 8:42

























                  answered Jul 31 '13 at 8:27









                  OR.OR.

                  5,19021437




                  5,19021437



























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