Inner Product

# Definition

The inner product between two vectors $\vec a$ and $\vec b$ is denoted by $\vec a \cdot \vec b$, and defined as some action between the vectors that follows the rules:

- $\vec a \cdot \vec a \geqslant 0$
- $\vec a \cdot \vec a = 0$ if and only if $\vec a = 0$
- $\alpha \vec a\cdot\vec b = \vec a\cdot\alpha \vec b = \alpha \left( {\vec a\cdot\vec b} \right)$, where $\alpha \in \mathbb{R}$
- $\vec a\cdot\left( {\vec b + \vec c} \right) = \vec a\cdot\vec b + \vec a\cdot\vec c$, where $\vec c$ is vector.
- $\vec a\cdot\vec b = \vec b\cdot\vec a$

Example:

page revision: 4, last edited: 23 Jul 2011 11:35