# Homework Help: Vector in three dimensions

1. May 16, 2007

### fffff

1. The problem statement, all variables and given/known data

Point A (2i +j 2k)
Point B (3i +2j +5k)
Point C (4i +5j -2k)

the point d is such that abcd in that order is a parallelogram.

Find position Vector D

2. Relevant equations

3. The attempt at a solution

ok so i start of like this but im getting the wrong answer.
http://img511.imageshack.us/img511/5946/vectorak5.jpg [Broken]

(BA)^1/2=(CD)^1/2

but its wrong.

Last edited by a moderator: May 2, 2017
2. May 16, 2007

### NateTG

It might be useful to make a drawing.

3. May 16, 2007

### fffff

Yes, but are those equations correct
I've realized my error.
culd you tell me the point of the unit vector.

Last edited: May 16, 2007
4. May 16, 2007

### NateTG

You don't need to do anything involving norms or unit vectors here, so the square root stuff is way off base. It's really just a matter of vector addition, and subtraction.

$$\vec{BA}=\vec{OD} - \vec {OC}$$
makes sense to me, the other equations don't really.