12.4 Similar Triangles and Similar Figures


Recall the meaning of similar—the shape is the same but the size may be different


Def. Scale Factor—ratio of the corresponding side lengths of a figure.















Def. Similar Triangles--∆ABC ~ ∆DEF iff A is congruent to D, B is congruent to E, C is congruent to F and .















AA versus AAA?????? –we only need two angles to prove similarity—this is if two angles of one triangle are congruent respectively to two angles of a second triangle, then the triangles are similar.










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