How can I determine the number of sides of the polygon

Answer 1

<svg height="210" width="500">
<polygon points="200,10 250,190 160,210" style="fill:lime;stroke:purple;stroke-width:1" />
</svg>

6 Entries in tag polygon attr. points.

6/2 = 3
therefore 3 sides

Answer 2

Martin Taylor
didn't take into account that two points might be the same😉
good aspect.