The SAS (Side-Angle-Side) criterion can be used to prove the similarity of two triangles by verifying that two sides of one triangle are proportional to two sides of the other triangle, and that the included angles between those sides are congruent. In other words, if you have two triangles, and you can show that:
- The lengths of two corresponding sides (let's call them \( a \) and \( b \) in one triangle, and \( c \) and \( d \) in the other) satisfy the proportionality condition \( \frac{a}{c} = \frac{b}{d} \).
- The angle that is formed between those two sides in both triangles is the same (let's denote this angle as \( \angle A \) in the first triangle and \( \angle B \) in the second triangle, and \( \angle A = \angle B \)).
If both of these conditions are met, then the two triangles are similar by the SAS criterion.