# Direction cosines and vectors

1. Sep 12, 2007

### tdusffx

I just started physics this year and having a difficult time, lol.

anyways, my question is:

suppose I was given a vector A, and A has x, y, z components of 4,6,3

How would I find its magnitude of A and the cosines of the angles that makes B?

2. Sep 12, 2007

### bel

It's like finding the length of a diagonal of a rectangle of length, breadth and depth of 4, 6, and 3 respectively, by the Pythagoras's theorem. And what's B?

3. Sep 12, 2007

### tdusffx

i'm sorry, I meant what are the angles that make vector A, sorry.

4. Sep 12, 2007

### tdusffx

also, i'm just wondering why I can't apply the formula Magnitude A = sqrt (x^2, y^2, z^2)

5. Sep 12, 2007

### robphy

By the way, your "vector" questions are MATH problems.
There's no physics yet. (Physics is not to blame.)

Are you looking for the "direction cosines"?
http://www.netcomuk.co.uk/~jenolive/vect7.html

6. Sep 12, 2007

### tdusffx

I just want to know if I use the |A| = sqrt (x^2 + y^2 + z^3)

7. Sep 12, 2007

### tdusffx

or the rectangular length like bel has mentioned above.

8. Sep 12, 2007

### Archduke

Yep, you can.

9. Sep 12, 2007

### tdusffx

hmm, ok thank you guys for the help.