A circle is indeed a polygon.
Define: Polygon
- A closed shape with more than two sides
Define: Side
- A straight line with a non-zero length
Define: Line
- The path between two points
Define: Point
A circle is said to have an infinite number of sides.
With that logic, the sides have zero length.
Because of this, a circle is not a polygon.
But wait. If all of the sides have zero length, then how is it possible for the circle to have a non-zero circumference?
A circle does not have an infinite number of sides, instead, it has tons and tons of lines.
Technically, a triangle is a very low quality circle. An octagon is closer, but not quite.
The more sides you add the closer to a circle you get. This is where the "infinite amount of lines" idea come from. Of course, there is a limit. There will come a point in time where adding another side does not change the appearance of the shape. At this point, you have achieved a circle.
As the resolution increases, so does the amount of sides required. But even our eyes can only register a certain amount of lines. Otherwise, we would see particles and atoms. The only way to that a circle would require an infinite number of lines would be at an infinite resolution. Seeing as the ladder cannot exist, neither can the former.