Definition:Similar Triangles

Definition
Similar triangles are triangles whose corresponding angles are the same, but whose corresponding sides may be of different lengths.


 * SimilarTriangles.png

Thus $\triangle ABC$ is similar to $\triangle DEF$:
 * $\angle ABC = \angle EFD$
 * $\angle BCA = \angle EDF$
 * $\angle CAB = \angle DEF$

Also see

 * Equiangular Triangles are Similar


 * The general definition of Similar Figures