1 for the polygon shown in figure on the next

Question

1. For the polygon shown in Figure on the next page, how many times will the vertex V₁ appear in the set of intersection points for the scan line passing through that point?  How many times will you count it when you form the pairs of intersection points? Justify your answer.

Answer: The vertex V₁ = V₄ will be counted once only since it is neither a maximum nor a minimum for y coordinates of the pairs of edges {V₀V₁,V₁V₂}and  {V₃ V₄ , V₄ V₅} .