The SAS (Side-Angle-Side) similarity criterion states that if two triangles have two pairs of corresponding side lengths that are proportional, and the included angles between those sides are congruent, then the triangles are similar.
This means that if you can demonstrate that:
- The lengths of two sides of one triangle are proportional to the lengths of the two corresponding sides of another triangle (i.e., the ratios of the two pairs of sides are equal),
- The angle between those two sides in one triangle is congruent to the angle between the corresponding sides in the other triangle,
then you can conclude that the two triangles are similar.
In summary, the SAS criterion guarantees similarity by confirming the proportionality of two sides and the congruence of the included angle.