The SAS (Side-Angle-Side) criterion can be used to prove the similarity of two triangles based on the following principles:
- Proportional Side Lengths: If two triangles have two pairs of corresponding sides that are in proportion (meaning the ratios of the lengths of those sides are equal), and the included angles (the angle formed between the two sides) between those sides are equal, then the triangles are similar.
In simpler terms, this means:
- If you have triangle \( ABC \) and triangle \( DEF \), and you know that:
- \( \frac{AB}{DE} = \frac{AC}{DF} \) (the ratios of the lengths of two corresponding sides are equal),
- The included angle \( \angle ABC = \angle DEF \) (the angle between those sides is equal),
then triangle \( ABC \) is similar to triangle \( DEF \) (written as \( \triangle ABC \sim \triangle DEF \)).
- Conclusion of Similarity: The similarity of the triangles implies that their corresponding angles are also equal and the lengths of corresponding sides are proportional, which can be used for further calculations or applications involving the triangles.
This criterion is particularly useful in cases where direct measurement of angles or the third side is not feasible, yet the relationship between side lengths and the included angles can be established, confirming the triangles' similarity.