Does the "by which" give correct meaning

Question

What clause should I use to express following idea correctly?

After that, polygon edges are extended and intersected by which leads a closed polygon.

Answer 1

I'm not sure, but I think this is an excerpt from construction rules of a polygon.

The by...which clause you have is neither grammatically correct nor meaningful. It can be one of these:

1. After that, polygon edges are extended and intersected by which we get closed polygon.
2. After that, polygon edges are extended and intersected which leads to a closed polygon.
3. After that, polygon edges are extended and intersected to construct a closed polygon.

There may be many more such possibilities, all depending on the text that preceded the excerpt.