Question

Find the angle between the given vectors to the nearest tenth of a degree.
u = <8, 4>, v = <9, -9>

Answer 1

\[u.v=\left| u \right|\left| v \right| \cos \theta \]
\[where~ \theta~is~the~\angle~\between~u~and~v \]

Answer 2

The quantity on the left side of this equation is the so-called DOT PRODUCT. I'd suggest you look this up and review it. In the same section you'll find a formula for the angle between two vectors. sshayer is correct. Can you take this info and come up with a solution now?

Hint: solve sshayer's equation for cos theta first.

find cost theta.

then use the inverse cosine function to determine the angle, theta.

Be careful: decide whether you want to work in degrees or in radians.

Answer 3

u.v=(8)(9)+(4)(-9)=72-36=?
\[\left| u \right|=\sqrt{8^2+4^2}=?\]
similarly find |v|
then proceed

Answer 4

so sqrt80 times sqrt162 cos x = 36?

Answer 5

Please show all details of your calculations here. Where did that sqrt 80 come from? sqrt 162?