Properties of Dot Product
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Theorem
Let $\mathbf u, \mathbf v, \mathbf w$ be vectors in the real Euclidean space $\R^n$.
The dot product has the following properties:
Dot Product with Self is Non-Negative
Let $\mathbf u$ be a vector in the real Euclidean space $\R^n$.
Then:
- $\mathbf u \cdot \mathbf u \ge 0$
where $\cdot$ denotes the dot product operator.
Dot Product with Self is Zero iff Zero Vector
- $\mathbf u \cdot \mathbf u = 0 \iff \mathbf u = \mathbf 0$
Dot Product Operator is Commutative
- $\mathbf u \cdot \mathbf v = \mathbf v \cdot \mathbf u$
Dot Product Operator is Bilinear
- $\paren {c \mathbf u + \mathbf v} \cdot \mathbf w = c \paren {\mathbf u \cdot \mathbf w} + \paren {\mathbf v \cdot \mathbf w}$
That last result is often broken down into two less powerful ones:
Dot Product Distributes over Addition
- $\paren {\mathbf u + \mathbf v} \cdot \mathbf w = \mathbf u \cdot \mathbf w + \mathbf v \cdot \mathbf w$
Dot Product Associates with Scalar Multiplication
- $\paren {c \mathbf u} \cdot \mathbf v = c \paren {\mathbf u \cdot \mathbf v}$