Swinging Door Help With Only A Script or Math Behind It?

So I like scripting for people for good practice and problem solving development but I cant for the life of me figure out how to make one of those doors that swing open using only a script. I've gone through so many forums but all they bring up are Motor's, Hinge doors, and other cheap methods. I know I'm supposed to at least add a little bit of code but I have nothing to show for but a lot of research. If anyone could explain to me how to make a door rotate on a specific axis such as the left or right side using only a script and help me understand the math behind it I'd be extremely grateful.