Vector Algebra

[tipping93]

Hi i need some help with this question.

if the position vectors of the points P and Q are i+3j-7k and 5i-2j+4k respectively, find PQ (this has an arrow above it pointing to the right) and determine its length and direction cosines.

In the answer it says PQ= (4,-5,11), and modulus of PQ= 9*square root of 2

I noticed Q-p= (4,-5,11) but im sure why they do this... please help!

 

[Deleted member 4993]

Hi i need some help with this question.

if the position vectors of the points P and Q are i+3j-7k and 5i-2j+4k respectively, find PQ (this has an arrow above it pointing to the right) and determine its length and direction cosines.

In the answer it says PQ= (4,-5,11), and modulus of PQ= 9*square root of 2

I noticed Q-p= (4,-5,11) but im sure why they do this... please help!

Do some Google search - for example with key-word "calculating vectors from two points"

For example you'll get following reference:

http://www.youtube.com/watch?v=gwk-XGfHR8U