# Homework Help: A little help, please

1. Jan 30, 2006

### xairylle

Hi, I'm Xairylle and I need a little help with this. I think it's kind of basic electromagnetics stuff but I don't know how this goes given that all I've got is a problem nothing else. I can't seem to get any of it and... it's not homework.

1. Express each of the given points into its equivalent vector
a) A(2,1,-5)
b) A(1,4,6) B(5,-3,0)

2. Find the lengths of the medians of the given triangles ABC
a) A(2,1,3) B(3,-1,-2) C(0,2,-1)

2. Jan 30, 2006

### Integral

Staff Emeritus
while this may not be homework, it is the sort of question which is very common in homework.

3. Jan 30, 2006

### lomantak

Each number in the bracket of three numbers is just representing a different dimension. E.g. $$(l, w, h)$$

4. Jan 31, 2006

### HallsofIvy

If by "equivalent vector" you mean what I would call "position vector" it is the vector pointing from the origin, (0, 0, 0), to the given point, (x, y, z) and is written as xi+ yj+ zk.

5. Feb 1, 2006

### prochatz

First of all, you must know 2 points (usually given) in order to create the specific vector. If so, the vector's coordinates are given by the coordinates of the second point minus the coordinates of the first.
For example, find the coordinates of the vector AB where A(1,-2,4) and B(2,2,-1).
It's obvious that AB(2-1,2+2,-1-4) ---> AB(1,4,-5)

In your first exercise, the position vector is asked. The position vector can be created by only knowing one point. The other point is always the origin point O(0,0,0).