Trigonometry for gaming: where to start?

Hi!

Browsing the forums, and during the development of games themselves, I'm realizing that a good knowledge of trigonometry is a great asset for creating professional games.

I would like to study trigonometry, strictly related to the topic of **game creation** (no need to master information outside that). Is there a comprehensive online guide or resource to read, which you would like to suggest?

I've already downloaded and read this from clickstore, http://clickstore.clickteam.com/math-and-loving-the-expression-editor, and it was very useful, but I would like to delve deeper into the matter.

Thank you,

Fabrizio