Finding Unit Vectors for Angle of pi/3 in R3

In summary, the problem is to find a unit vector x in R3 that makes an angle of pi/3 with each of the vectors (1,0,-1) and (0,1,1). The hint is to use dot product to find the angle between vectors. The three constraints on the solution vector are: unit vector, specified angle with a vector, and specified angle with another vector. This can be translated into three equations with three unknowns (a,b,c) which can be solved to find the correct answer of (1/sqrt(2), 1/sqrt(2), 0).
  • #1
gunnar
39
0
There are two vectors (1,0,-1) and (0,1,1)
I need to find all the unit vectors x in R3 that make an angle of pi/3 with each of the vectors above.

Can someone please help with this problem?
 
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  • #2
hint:
use dot product to find the angle between vectors
 
  • #3
You should be able to use the three constraints on your solution vector (unit vector, specified angle with a vector, specified angle with another vector) to write down three equations in the components of your solution vector. Then, solve.
 
  • #4
O.K I figured out that the angle between the given vectors is 60 degrees or pi/3

The angle between the unit vectors and each of the given vectors is supposed to be pi/3 also. So I used the dot product to calculate

c=sqrt(2) since the unitvector has length 1 and both the given vectors have the length sqrt(2)

Don't seem to be able to get the right answear.
The correct answear is (1/sqrt(2), 1/sqrt(2), 0) only one vector.

How to reach that conclusion I have no idea
 
  • #5
Lets call the components of the vector you seek (a,b,c). Now there are three restriction on these three numbers. So when you write down the tree restrictions Hurkyl gave in terms of a,b and c you have three equations with three unknowns which you can solve. Can you translate the restrictions from words to algebra?
 

FAQ: Finding Unit Vectors for Angle of pi/3 in R3

What are unit vectors in R3?

Unit vectors in R3 are vectors with a magnitude of 1 that point in a specific direction in three-dimensional space. They are commonly used in mathematics and physics to represent directions and orientations.

How do you find the unit vector for an angle of pi/3 in R3?

To find the unit vector for an angle of pi/3 (60 degrees) in R3, you can use the following formula:

u = (cos(pi/3), sin(pi/3), 0)

This will give you a unit vector pointing in the direction of pi/3 in the x-y plane.

Why is it important to find unit vectors in R3?

Unit vectors in R3 are important because they allow us to represent directions and orientations in three-dimensional space. They are also useful for calculating vector operations and solving problems in physics and engineering.

Can you have multiple unit vectors for the same angle in R3?

Yes, it is possible to have multiple unit vectors for the same angle in R3. This is because there are infinitely many unit vectors in any given direction in three-dimensional space.

How do you know if a vector is a unit vector in R3?

To determine if a vector is a unit vector in R3, you can calculate its magnitude using the Pythagorean theorem. If the magnitude is equal to 1, then the vector is a unit vector. Additionally, the vector's components should have a ratio of 1:1:1 (x:y:z) to be considered a unit vector in R3.

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