
 All Elementary Mathematics  Study Guide  Geometry  Polygon... (Site not responding. Last check: ) 
  A, angles of polygon; segments AC, AD, BE etc. are diagonals; AB, BC, CD, DE, EF, FA – sides of polygon; a sum of sides lengths AB + BC + … + FA is called a perimeter of polygon and signed as p (sometimes – 2p, then p – a halfperimeter). 
  A hexagon on Fig.17 is a convex one; a pentagon ABCDE on Fig.19 is not a convex polygon, because its diagonal AD lies outside of it. 
  A sum of interior angles in any convex polygon is equal to 180 (n – 2) deg, where n is a number of angles (or sides) of a polygon. 
 www.bymath.com /studyguide/geo/sec/geo6.htm (207 words) 
