vector eqn problem [Archive]

jean014

Oct1-07, 05:45 AM

jean014

Oct1-07, 09:02 AM

hello!

im new here and i just need a little help in solving this problem:
its a set of vector equation:
1. The problem statement, all variables and given/known data

A = ai + bj + cK
B = -2i +j - 4K
C = i + 3j +2k

where A is an unknown vector. If

(AxB)+(AxC) = (5a + b)i + (3b-2)j + (-4c+1)k

i need to solve for a,b,c..

2. Relevant equations

matrix inversion by co-factor mtd or LU decomp..

3. The attempt at a solution

i dont even know where to begin!

pls pls pls help..

just on how to start .. or the algo ill finish the rest >.<

thnx!

D H

Oct1-07, 09:42 AM

To start you should calculate A\times(B+C). You know B and C and have an expression for A.

HallsofIvy

Oct1-07, 10:05 AM

hello!

im new here and i just need a little help in solving this problem:
its a set of vector equation:

A = ai + bj + cK
B = -2i +j - 4K
C = i + 3j +2k

where A is an unknown vector. If

(AxB)+(AxC) = (5a + b)i + (3b-2)j + (-4c+1)k

i need to solve for a,b,c..

pls pls pls.. help! >.<

thanks
Looks a lot like homework to me- so I'm going to move it to the "Homework- calculus and beyond" folder.

And, of course, you will have to make an effort yourself: What are AxB and AxC? That should be your first step. Then add those two and set them equal to the right hand side above. That will give you three equations to solve for a, b, c.

D H

Oct1-07, 10:18 AM

This is exactly the same problem as this thread (http://www.physicsforums.com/showthread.php?t=188267). They should be merged. Jean, you are not supposed to post the same thing in multiple threads.

HallsofIvy

Oct1-07, 02:51 PM

This is exactly the same problem as this thread (http://www.physicsforums.com/showthread.php?t=188267). They should be merged. Jean, you are not supposed to post the same thing in multiple threads.
Thanks. I will.

(It was in "Engineering, Computer Science, and Technology"?? No wonder I didn't find it!)