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Euclid Book 1 - Proposition 4
Congruent triangles if two sides and included angle are equal


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To be proved: If two triangles have two sides equal to two sides respectively, and have the angles contained by the equal straight lines equal, then they also have the base equal to the base, the triangle equals the triangle, and the remaining angles equal the remaining angles respectively, namely those opposite the equal sides.

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There are two triangles ABC and DEF where line AB = DE, line AC = DF and angle BAC = EDF
 
  
  
  
  
  
  

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