Linear Algebra: find a unique vector v given two other vectors related to v

In summary, the unique vector v=[v1,v2,v3] that satisfies the given conditions is v=[1/√3,2/√3,0].
  • #1
greenclipboar
2
0

Homework Statement


Let u=[1,1,-1] and w=[2,4,2].
Find the unique vector v=[v1,v2,v3] such that:
v.u=1
v is orthogonal to w
|v|=sqrt(3)
v2 > 0


Homework Equations


v.u=|v||u|cos(theta)


The Attempt at a Solution


I've just been blindly solving different aspects of this, but have no idea how to put it all together.

w.v=0

u.w=4

v.u=v1+v2-v3=1

|v|=sqrt(3) = sqrt(v1^2+v2^2+v3^2) therefore v1^2+v2^2+v3^2 = 3

cos(theta) between u and v is 1/3

cos(theta) between w and v is 1/sqrt(6)
 
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  • #2
Never mind, I figured it out. You solve for v1 and v3 using the above relations, then plus both of those into v1^2+v2^2+v3^2 = 3 to get a quadratic only using v2.
The solve for v2 (only the positive answer) which you sub into any equation to find v1 and v3.
 

1. How do I find a unique vector v given two other vectors?

To find a unique vector v, you can use the formula v = a + b, where a and b are the two given vectors. This will give you a third vector that is unique and related to the original two vectors.

2. Can I use any two vectors to find a unique vector v?

No, in order for the vector v to be unique, the two given vectors must be linearly independent. This means that they cannot be multiples of each other and must have different directions.

3. What is the significance of finding a unique vector v?

Finding a unique vector v allows you to solve for a specific solution to a system of linear equations. This can be used in various applications, such as computer graphics and engineering problems.

4. Are there any other methods to find a unique vector v?

Yes, there are other methods such as using the cross product or the Gram-Schmidt process. However, the formula v = a + b is the simplest and most commonly used method.

5. Can a unique vector v be found if the two given vectors are in different dimensions?

No, in order for the formula v = a + b to work, the two given vectors must be in the same dimension. Otherwise, the vector v will not be unique and the formula cannot be applied.

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