State SAS similarity criterion.

SAS Similarity Criterion: If in two triangles, one pair of corresponding sides are proportional and the included angles are equal then two triangles are similar.

In ΔABC and ΔDEF, if

$\frac{\mathrm{AB}}{\mathrm{DE}}=\frac{\mathrm{AC}}{\mathrm{DF}}$ and

$\angle \mathrm{A}=\angle \mathrm{D}$

Then, $\triangle \mathrm{ABC} \sim \triangle \mathrm{DEF}$