http://web2.0calc.com/questions/a-a-regular-nonagon-9-sided-polygon-is-inscribed-in-a-circle-as-shown-below-three-of-the-9-vertices-are-selected-at-random-and-the-tri
+118608 Maybe another mathematician would like to give this one a shot?
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You are not dumb, I didn't answer it because it was hard and i was short of time.
Maybe I could not have answered it. 
Maybe if you play around with part A and really underfstand it, you will be able to figure out part b just as easily as I could.
I will see if time allows me to look at it more.
I think a formula for an odd number of sides shouldn't be too hard to develope from what i have done but maybe it is different for an even number of sides.
I put that first line there to try and attract others to take a look.
