# Computing tangential and radial vector components of linear acceleration

I have to show that the tangential and radial vector components of linear acceleration are given by:

$$\bar a_{\rm{tan}}=\bar a \times \bar r \;\;\; \bar a_R=\bar w\times\bar v$$

I'm having a hard time with this one since it is using the cross-product and I have only just learned this concept. I'm not sure what vectors to cross.

Thanks for any help, and sorry I can't give you any of my work, but I can't find the information needed to be able to cross those vectors.

EDIT: Also, this is assuming this is a rigid object rotating about a fixed axis, in case that helps at all. I still don't know how to show this and I have looked at the text but can't find any examples or ideas on how to do this. Again, I appreciate any help.