# Math Help - Proof (vectors, norm, and dot product)

1. ## Proof (vectors, norm, and dot product)

Never-mind, I found the problem.

2. Originally Posted by elitethut
Hi everyone !

I want to solve the following:

$1/4||\vec{u}+\vec{v}||^2-1/4||\vec{u}-\vec{v}||^2=\vec{u} \cdot \vec{v}$

I have no idea how to start this proof...anyone can help ??

Thanks !

Definition: $||\vec{u}||^2:=\vec{u}\cdot \vec{u}$, so now you have an idea how to begin here.

Tonio

3. Originally Posted by elitethut
Hi everyone !

I want to solve the following:

$1/4||\vec{u}+\vec{v}||^2-1/4||\vec{u}-\vec{v}||^2=\vec{u} \cdot \vec{v}$

I have no idea how to start this proof...anyone can help ??

Thanks !

Nevermind. I think I goofed.