# Homework Help: Vector Multiplication

1. Mar 27, 2017

### influx

1. The problem statement, all variables and given/known data

2. Relevant equations

RAO = b(Sinβj+Cosβk)

3. The attempt at a solution

The box in red is ω. However I am unsure of where they got the box in blue from? As mentioned above, RAO = b(Sinβj+Cosβk) so not sure where they got the box in blue from? I know of the vector triple product: A x (B x C) = (A•C)B - (A.B)C, but this isn't what they've done?

Thanks

2. Mar 27, 2017

### pasmith

I would assume that they are doing the obvious thing, ie. calculating $\mathbf{\omega} \times \mathbf{r}_{AO}$ first, and given the presence of a scalar factor of $b$ (which goes missing in the second line before reappearing in the third) the vector in the blue box must therefore be $$\frac{\mathbf{\omega} \times \mathbf{r}_{AO}}{b}.$$ (Although given that something did go missing partway through I would recommend double-checking this.)

Last edited: Mar 27, 2017