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Two linear algebra questions - Vector geometry

  • Thread starter ElliottG
  • Start date
  • #1
24
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Homework Statement


[URL]http://184.154.165.18/~devilthe/uploads/1321855187.png[/URL]


Homework Equations


No idea.


The Attempt at a Solution


Alright...so really no idea what to do here...never did any examples like this in class and have scoured over my notes for 2 hours now trying to figure this out...and can't lol.

I tried finding the vector UV and then finding a vector that is orthogonal to that with no success...

Homework Statement


[URL]http://184.154.165.18/~devilthe/uploads/1321923155.png[/URL]


Homework Equations


Included?


The Attempt at a Solution


Homework Statement





Homework Equations





The Attempt at a Solution


Again, not much clue on what to do here...actually no clue at all :(

I know it sounds like I'm trying to freeload but I've already completed 7/9 of my other homework questions it's just these two that I have no idea how to do...
 
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Answers and Replies

  • #2
378
2
Have you guys covered cross products yet?
 
  • #3
24
0
No we have not...I saw that on another site as an answer to this question but had no idea how they got the answer.
 
  • #4
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,071
Let the vector you seek be [x1 y1 z1]
As it is perpendicular to [3 -10 4], by calculating the dot product
we can say 3.x1 -10.y1 + 4.z1 = 0
... and similarly for the second vector.

We now have 2 equations in 3 unknowns.
So let z1 be any convenient value, I chose z1 = 1.
Solve for x1 and y1.

Check that the resultant vector is perpendicular to both of the given vectors.
 
  • #5
24
0
Thanks Nascent, got it!
 
  • #6
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,071
Maybe then try it with z1=2, and comment on what you discover.
 

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