# Double modulus sign?

1. Apr 1, 2012

### hivesaeed4

I'm confused regarding why the double modulus sign is used. Let's take the dot product:

u.v=|u||v|cosθ The R>H>S means that the cosine of the angle is multiplied witht the magnitudes of both vectors.
Now,
u.v=||u||||v||cosθ
Does this mean the same thing? Help?

2. Apr 1, 2012

### chiro

Typically when you see ||a|| it refers to a norm or length of a vector just for future reference. In this case it means the same thing, but in other contexts it may not.

Whenever you look at geometry and you see ||a||, then this will refer to norms and if people need to refer to distance and the space is a norm then this will be used.

3. Apr 1, 2012

Thanks