# Scalar product of vectors

1. Apr 4, 2010

### lypaza

[PLAIN]http://img62.imageshack.us/img62/5319/49966749.png [Broken]

What is the scalar multiples of a vector actually?
I was thinking L = c[2 1 2]T
Then I looked for projection of v on L. But I got c in my answers which are not supposed to be...

Last edited by a moderator: May 4, 2017
2. Apr 4, 2010

### Staff: Mentor

Every vector in L is some scalar multiple of <2, 1, 2>. The line goes through the origin - the zero multiple of this vector is 0<2, 1, 2> = <0, 0, 0>, a vector that starts and ends at the origin. The line goes through the point (-4, -2, -4), which you can get by taking the -2 multiple of the vector.

For the reflection of v in the line, you want to find another vector w that is in the same plane as v and L, but is on the opposite side of L, and makes the same angle with L.

Last edited by a moderator: May 4, 2017
3. Apr 4, 2010

### lypaza

So I have to find angle theta between v and L, and then find vector w with negative theta?
I also have to find the plane of v and L by cross product of v and L ....

Last edited: Apr 4, 2010