
 Symmetry and Polygons 
  Triangles, as mentioned in Numbers lesson 11 and Geometry lesson 2, can be classified either by the number of sides with the same length (0 is scalene, 2 or more is isosceles, all 3 is equilateral) or by the largest angle (acute, right, obtuse). 
  In an isosceles triangle, the bisector of the vertex angle, 
  Although the line of symmetry of an isosceles triangle is an angle bisector, median, perpendicular bisector, and an altitude, in most triangles, these lines are different. 
 www.andrews.edu /~calkins/math/webtexts/geom06.htm (2449 words) 
