# Math Help - vectors

1. ## vectors

If two vectors u and v fit the equation (u - v) times (u - v) = u times u + v times v, how must these vectors u and v be related? What familiar theorem does this equation represent?

2. Is this the problem: $\left( {u - v} \right) \cdot \left( {u - v} \right) = u \cdot u + v \cdot v$?
That is dot product, not times.

3. Originally Posted by Plato
Is this the problem: $\left( {u - v} \right) \cdot \left( {u - v} \right) = u \cdot u + v \cdot v$?
That is dot product, not times.
Yes it is. Sorry I didn't know how to do dots, so I just put the x in instead. I should have specified.

Can you help me? =(

4. $\left( {u - v} \right) \cdot \left( {u - v} \right) = u \cdot u - 2u \cdot v + v \cdot v$
but if that is $u \cdot u - 2u \cdot v + v \cdot v = u \cdot u + v \cdot v$
do you see that $2u \cdot v = 0$?
So what does that mean about u & v?