geometry angle symbol, can it be typed? which font or keyboard character?

In the app you are in click on the space where you want the charter then click the edit menu then select special characters then select math in the left of the window the find the symbol and click on it to insert. http://docs.info.apple.com/article.html?path=Mac/10.4/en/mh1064.html

It's Unicode 2220, which you can find via Character Viewer (Edit > Special Characters): ∠∠∠