# Math Help - Cross product

1. ## Cross product

how do you perform the cross product on something like this? $\begin{bmatrix} c& s & 0 & \\ -s &c & 0 & \\ 0& 0& 1& \end{bmatrix}$ X $\begin{bmatrix} x&\\ y &\\ 1 & \end{bmatrix}$

2. Originally Posted by p00ndawg
how do you perform the cross product on something like this? $\begin{bmatrix} c& s & 0 & \\ -s &c & 0 & \\ 0& 0& 1& \end{bmatrix}$ X $\begin{bmatrix} x&\\ y &\\ 1 & \end{bmatrix}$

3x3 X 3x1 = 3x1 so

$\begin{bmatrix} c & s & 0 \\ -s & c & 0 & \\ 0 & 0 & 1 & \end{bmatrix} \times \begin{bmatrix} x \\ y \\ 1 \end{bmatrix} = \begin{bmatrix} cx+sy \\ -sx +cy \\ 1\end{bmatrix}$