**Similarity** is when two or more geometric shapes are of the same shape. These shapes are said to be similar. Similar shapes are identical in all senses except size.

## Proving Triangles are Similar

There are many ways of proving that two triangles are similar. The ways of proving the similarity of two triangles are the following:

**AA**or Angle-Angle. If two angles of each triangle are congruent, then the two triangles are similar.**SSS**or Side-Side-Side. If the lengths of the corresponding sides of two triangles are proportional, then the triangles are similar.**SAS**or Side-Angle-Side. If an angle of one triangle is congruent to an angle of a second triangle and the lengths of the sides including these angles are proportional, then the triangles are similar.

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