Linear Algebra - Projection of Vector

In summary, the question is about finding the projection of vector u perpendicular to vector v. The attempt at a solution involves finding the projection of u in the direction of v and then using trigonometry to find the perpendicular component. The asker initially doubted the answer key, but later realized it was correct.
  • #1
YoshiMoshi
224
8

Homework Statement



I feel like this is a easy question but it seems the answer key doesn't seem to be right.

So say I have 2 vectors

equation 1.PNG


and I'm trying to find the projection of vector u perpendicular to the vector v

Homework Equations

The Attempt at a Solution



So I don't remember doing something like this before but I would assume that I start off by finding the projection of u in direction of v

equation 2.PNG

alright so this gives me
equation 3.PNG


So conceptually thinking I see that I have a vector u and a vector V|| sort of like this

IMG_20160408_153526779.jpg

So I can find the angle between u and V and I get 104.963 degrees

IMG_20160408_153856303.jpg


So to get the perpendicular component is it just

tan(theta) = (V perpendicular)/(V parallel)
so V perpendicular is
(V parallel)tan(theta) = V perpendicular?

IMG_20160408_154414914.jpg


I think is conceptually ok but I'm not sure because my answer key does V - V parallel which would appear to be wrong in my opinion because I don't see how that would give us V perpendicular, unless I'm not understanding what vector I'm looking for.

Thanks for any help.
 
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  • #2
I see that apparently the answer key is correct and see why never mind
 

1. What is a projection of a vector in linear algebra?

A projection of a vector in linear algebra is the process of finding the closest vector in a subspace to the original vector. It involves creating a new vector that is perpendicular to the subspace and has the same direction as the original vector.

2. How is the projection of a vector calculated?

The projection of a vector is calculated by using the dot product between the original vector and a unit vector in the direction of the subspace. The resulting scalar is then multiplied by the unit vector to obtain the projected vector.

3. What is the purpose of projecting a vector in linear algebra?

The purpose of projecting a vector in linear algebra is to find the closest approximation of the original vector in a lower-dimensional subspace. This can be useful in data analysis, image processing, and solving optimization problems.

4. How does the projection of a vector affect its length and direction?

The projection of a vector does not change its length, but it does change its direction. The projected vector will be parallel to the subspace, while the original vector may not be. Additionally, the projected vector and the original vector will be orthogonal to each other.

5. Can a vector be projected onto any subspace in linear algebra?

No, a vector can only be projected onto a subspace that is perpendicular to the vector's direction. This means that the subspace must be orthogonal to the original vector in order for a projection to be possible.

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