Iner product

Triple product expansion
Main article: Triple product

This is a very useful identity (also known as Lagrange’s formula) involving the dot- and cross-products. It is written as

\mathbf{a} \times (\mathbf{b} \times \mathbf{c}) = \mathbf{b}(\mathbf{a}\cdot\mathbf{c}) - \mathbf{c}(\mathbf{a}\cdot\mathbf{b})

which is easier to remember as “BAC minus CAB”, keeping in mind which vectors are dotted together. This formula is commonly used to simplify vector calculations in physics.

From http://en.wikipedia.org/wiki/Dot_product

Nhiều tính chất khác tại http://en.wikipedia.org/wiki/Cross_product
It is not associative, but satisfies the Jacobi identity:

\mathbf{a} \times (\mathbf{b} \times \mathbf{c}) + \mathbf{b} \times (\mathbf{c} \times \mathbf{a}) + \mathbf{c} \times (\mathbf{a} \times \mathbf{b}) = \mathbf{0}.

One Response to “Iner product”

  1. vanchanh123 Says:

    Ngoài tên gọi trên thì công thức trên còn có tên là R…?


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