
 Triangle  LearnThis.Info Enclyclopedia (Site not responding. Last check: 20071102) 
  That is, if the longest side of a triangle is twice that of the longest side of a similar triangle, say, then the shortest side will also be twice that of the shortest side of the other triangle, and the median side will be twice that of the other triangle. 
  The crucial fact is that two triangles are similar if and only if their corresponding angles are equal, and this occurs for example when two triangles share an angle and the sides opposite to that angle are parallel. 
  This is also the triangle's center of gravity: if the triangle were made out of wood, say, you could balance it on its centroid, or on any line through the centroid. 
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