1. ## Vector

The point A and B have coordinates (2,3,-1) and (5,-2,2) respectively. Calculate the acute angle between AB and the line with equation

All i need to know is which two to multiply
e.g: (x,y,z) x (x1,y1,z1)
(MY PROBLEM IS HOW TO FIND OR WHICH TWO POINTS TO MULTIPLY)

the i know how to continue

2. Originally Posted by manutd4life
The point A and B have coordinates (2,3,-1) and (5,-2,2) respectively. Calculate the acute angle between AB and the line with equation r=(2,3,-1)+t(1,-2,2), giving your answer correct to the nearest degree.
The angle is $\displaystyle \arccos \left( {\frac{{\left| {\overrightarrow {AB} \cdot D} \right|}}{{\left\| {\overrightarrow {AB} } \right\|\left\| D \right\|}}} \right)$ where D is the direction vector of the line.

3. is AB=AO+OB
=(-2,-3,1)+(5,-2,2)
=(3,-5,3)

let x=(3,-5,3) and y=(1,-2,2)

(3,-5,3).(1,-2,2)
=3+10+6
=19

so i use |x|.|y|.cos o=19

Is this good plz help

4. Originally Posted by manutd4life
is AB=AO+OB
=(-2,-3,1)+(5,-2,2)
=(3,-5,3)
NO! $\displaystyle \overrightarrow {AB} = \left\langle {5, - 5,3} \right\rangle$

Surely you know how to find the vector determined by two points?

5. can u explain how u got this plz, cause i forgot a bit

6. Originally Posted by manutd4life
can u explain how u got this plz, cause i forgot a bit
$\displaystyle P:\left( {p_1 ,p_2 ,p_3 } \right)\;\& \,Q:\left( {q_1 ,q_2 ,q_3 } \right)\, \Rightarrow \,\overrightarrow {PQ} = \left\langle {q_1 - p_1 ,q_2 - p_2 ,q_3 - p_3 } \right\rangle$

7. can u tell me what the answer??

8. Originally Posted by manutd4life
can u tell me what the answer??
Sorry, but no I cannot. I am not willing to do the tedious work it takes.