A polyline is an irregular curve composed of line segments, and it is a geometric figure in which many line segments end in turn and are not on the same line. If the starting point and ending point of a polyline coincide, it is a closed polyline, most commonly a polygon. If the starting point and the ending point do not coincide, it is a polyline, just like a polyline in a line chart.

Usually we study geometric figures, such as rectangles, isosceles triangles, parallelograms and so on. In fact, it is equivalent to studying right-angled polylines, equilateral or equilateral polylines, parallel polygonal polylines, etc. It can also be seen everywhere in our lives. The line chart of our research data also uses its characteristics to represent numerical trends and trend changes.