Mathematics

Problem

\mathbf{r}(t) = \mathbf{a} \cos \omega t + \mathbf{b} \sin \omega t

, where

\mathbf{a}

and

\mathbf{b}

are constant vectors, show that

\mathbf{r}(t) \times \mathbf{r}'(t) = \omega \mathbf{a} \times \mathbf{b}