Identifying Concave Polygons Characteristics e At least one interior angle >1800 >180° Extension of some edges intersect other o Line segment of some pair of interior points intersects the be Doundary Mathematically The cross products of adjacent edges Convex: the same sign (E1XE2)>0 Concave: some are positive and (E2×E3)2>0 (E3×E4)2<0 some are negative (E4×E5)2>0 (next slide for the detail) (E3×E)2>0 (E6×E1)2>0Identifying ConcavePolygons  Characteristics  At least one interior angle>180o ;  Extension of some edges intersect other;  Line segment of some pair of interior points intersects the boundary.  Mathematically  The cross products of adjacent edges  Convex: the same sign  Concave: some are positive and some are negative (next slide for the detail ) 8