How to identify four sided polygon (not rectangle) collision detection?

I am 开发者_如何转开发developing 2D game for iPhone, for that I need to handle collision detection.

My need is: I have two polygons, each is a four-sided polygon (not a rectangle), I need to check whether they are collided or not.

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See a good tutorial at CodeProject: http://www.codeproject.com/KB/GDI-plus/PolygonCollision.aspx