Lagrange's Formula/Corollary

Theorem
Let:


 * $\mathbf a = \begin{bmatrix} a_x \\ a_y \\ a_z \end{bmatrix}$, $\mathbf b = \begin{bmatrix} b_x \\ b_y \\ b_z \end{bmatrix}$, $\mathbf c = \begin{bmatrix} c_x \\ c_y \\ c_z \end{bmatrix}$

be vectors in $\R^3$.

Then:
 * $\left({\mathbf a \times \mathbf b}\right) \times \mathbf c = \left({\mathbf{a \cdot c} }\right) \mathbf b - \left({\mathbf{b \cdot c} }\right) \mathbf a$