- #1
Saladsamurai
- 3,020
- 7
Homework Statement
I am following along in a book and in one line the author asserts that
[tex](\mathbf{A}\times\mathbf{B})\cdot(\mathbf{C}\times\mathbf{D}) = (\mathbf{A}\cdot\mathbf{C})(\mathbf{B}\cdot\mathbf{D}) - (\mathbf{A}\cdot\mathbf{D})(\mathbf{B}\cdot\mathbf{C})\qquad(1)[/tex]
Homework Equations
I believe that he is somehow using the rule that
[tex]\mathbf{A}\times(\mathbf{B}\times\mathbf{C}) = \mathbf{B}(\mathbf{A}\cdot\mathbf{C}) - \mathbf{C}(\mathbf{A}\cdot\mathbf{B})\qquad(2)[/tex]
The Attempt at a Solution
Is this the only rule he is using to arrive at (1) ?
I am having trouble see how to implement this to arrive at the same result. Am I missing something painfully obvious?