Problem 2.1: Is the following polygon convex or concave? [Solution]

Problem 2.2: Is the following polygon convex or concave? [Solution]

Problem 2.3: Is the following polygon convex or concave? [Solution]

Problem 2.4: Is the following polygon convex or concave? [Solution]

Problem 2.5: A line l is the perpendicular bisector of one side of a regular polygon. Besides the midpoint of the bisected segment, where does l intersect the polygon? [Solution]