SAS Similarity
Definition
AoPS
SAS stands for Side-Angle-Side, for two triangles to be similar triangles by SAS similarity, they must have a pair of congruent angles and the two sides next to the angle must be proportional.
Mathwords Definition
Side-angle-side similarity. When two triangles have corresponding angles that are congruent and corresponding sides with identical ratios as shown below, the triangles are similar.
Diagram
![[asy] dot((0,0)); label("A",(0,0),SW); dot((5,0)); label("B",(5,0),SE); dot((3,4)); label("C",(3,4),N); draw((0,0)--(5,0)--(3,4)--cycle); markscalefactor = 0.1; draw(anglemark((5,0),(0,0),(3,4))); [/asy]](http://latex.artofproblemsolving.com/1/7/8/17873a662288147a81102d3f98300c4e3d7f4817.png)
![[asy] size((8cm)); dot((0,0)); label("D",(0,0),SW); dot((5,0)); label("E",(5,0),SE); dot((3,4)); label("F",(3,4),N); draw((0,0)--(5,0)--(3,4)--cycle); markscalefactor = 0.0675; draw(anglemark((5,0),(0,0),(3,4))); [/asy]](http://latex.artofproblemsolving.com/9/8/4/984781cf0bae47382fd022cb1da382c723e8fbdf.png)
If 
and 
, then the triangles are similar by SAS similarity.
