# Dot product vectors

1. Nov 9, 2008

### ih8calc

Hello, I have this problem that asks the following

1. The problem statement, all variables and given/known data
Find two vectors v1 and v2 whose sum is (-1,0) where v1 is parallel to (5,-5) while v2 is perpendicular to (5,-5).

Could someone "walk" me thought the steps to find v1 and v2... I'm confident I can make the computations is the steps that are unknown to me... thanks in advance...
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 9, 2008

### Phrak

If v1 is parallel to (5,-5) then v1 = (k5,-k5). k is an unknown that you will need to solve for.

A similar setup applies to v2. v2 is perpendicular to (5,-5) so it is parallel to (5,5).

3. Nov 9, 2008

### gabbagabbahey

The first step would be to write the unknown vectors in terms of there unknown components: $v_1=(x_1,y_1)$ and $v_2=(x_2,y_2)$...what is $v_1+v_2$ in terms of these components?...what does the fact that this vector sum must be (-1,0) tell you?

4. Nov 9, 2008

### ih8calc

....okay, so maybe I can't follow directions as well as I thought... I hate to ask, but could you solve it for me? it's one of those things where I'm just stumped...

5. Nov 9, 2008

### gabbagabbahey

Why don't you show us what you've got? (even if you think it is wrong)

6. Nov 9, 2008

### HallsofIvy

Staff Emeritus
Since you titled this "dot product" why don't you tell us what you think the dot product is and how it is related to "perpendicular".