# Thread: find angle between vectors .. confusion.

1. ## find angle between vectors .. confusion.

u * v / |u| |v| = cos theta

how is -14/39 = cos theta = 1.94?

if -14/(13 * 3) = cos theta

please help if this makes any sense.

find the angle between u and v give your answer to the nearest .01 radians.

2. Originally Posted by rcmango
...

if -14/(13 * 3) = cos theta

...

Hello,

you have: cos(θ) = -14/39. Now use the arccos-function:

arccos(-14/39) = 1.9379651...

EB

3. Originally Posted by rcmango
-14/39 = cos theta = 1.94
Pet Peeve alert!

Are you seriously suggesting that -14/39 = 1.94 ?? Be careful of what you write. Students have lost points on tests for less!

-Dan