Year 8 maths Homework and the internal angles of a polygon.....done.

The night before last I helped my son with his maths homework. He is in year 8 and it consisted of working out the angles of some shapes, mostly triangles within polygons.I enjoyed it - its like a puzzle and when you get the first couple the others come like a waterfall of knowledge.

However, the next part was not quite as easy. You had to work out the internal angles of a nonagon - a nine sided shape. Well, I just did not know how to do it and it frustrated me. In the end we had to give up. The next day I was on a mission to work them out. Am I slightly obsessive....?

I asked people in my staff room, but nobody seemed to know. Then I googled nonagon and found the most interesting site. It gave me a formula which I could use to work out the internal angles of any polygon. Why I would want or need to do that is a mystery, but if I am ever called upon in the course of my everyday life to work out the internal angles of any multi sided shape, be it regular or irregular, I am now equipped with the knowledge to do so.

You need the equation:   180(n-2)      

This means that, taking n as the number of internal angles, you take 2 away from it then multiply by 180.

So.... a nonagon.... a nine sided shape is 9-2 then x180....  so 7 x 180 which = 1260.

My thirst for knowledge is satisfied. All I need now is somebody to desperately need to know the total of the internal angles of ...... something.

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