## anonymous one year ago Two vector A=(3, 4, -5) and B=(-1, 1, 2). Determine the magnitude of A+B and the direction (angle) of A+B ?

1. misty1212

HI!!

2. misty1212

did you find $$A+B$$?

3. anonymous

Yes, it is $\sqrt{38}$ and the angle I found is 121 but the answer it the book says it is 71 =(

4. misty1212

oh how did you find the angle (i actually am not sure what angle means in three dimensions)

5. anonymous

A.B( dot product) = $\left| A \right|.\left| B \right|$ .cos

6. misty1212

doesn't that find the angle between the two vectors?

7. anonymous

Yes, think the book has the wrong answer! thank you anyway ^^