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# How points around a polygon are labelled

Hi,

Coming from the UK, I have seen a lot of variation of the definitions that I am used to. One that I am yet to get my head around is how the points are labelled in a polygon. For example, in a square, I would label, starting from the top left and going clockwise. However, reading further on in the problem, it turns out that I should've started in the top left and then the top right, bottom left and bottom right. Is there a universal point labelling method on brilliant or does it vary by problem?

Note by Lewis Tough
4 years, 7 months ago

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Oh okay, I've usually labelled from the top left and clockwise, I'll give your method a try, thanks!

- 4 years, 7 months ago

Points are labelled in order. It doesn't matter whether you use clockwise or anti clockwise (unless otherwise stated). It doesn't matter where you chose to start. Your answer should stay the same, even if your friend is looking at your diagram from across the table, or if you are looking at it's reflection in a mirror.

For example, if you are told that $$ABCD$$ is a square, then as long as $$A$$ and $$C$$ are opposite, and $$B$$ and $$D$$ are opposite, that's fine. It doesn't matter if $$A$$ is in the bottom left, or if $$A$$ is in the top left. $$B$$ has to be next to it, and the rest of the vertices should follow in order.

Could you state / link the problem which you are referring to? I'd check the writeup and see if the vertices were wrongly labelled.

Staff - 4 years, 6 months ago

It was one from last week I think, I'll try and find it.

- 4 years, 6 months ago

This is what's told me on high school to be universal: start in the bottom left and go anti-clockwise. In some polygons, it is not obvious what the bottom left is (e.g. a regular hexagon), so I just pick one. I have never seen some polygon being labeled like you described (zigzagging), all labelings that I've seen go around the polygon only.

- 4 years, 7 months ago