Now from the given figure it can be seen that in ΔXYZ and ΔVWZ
∠WZY=∠WZY [<em>Vertically opposite angles are equal]</em>
Also,
Therefore by SAS criteria of similarity, ΔXYZ and ΔVWZ are similar triangles.
SAS similarity theorem says that if an angle of a triangle is equal to an angle of a another triangle and the lengths of the sides including these angles are proportional, then the triangles are similar.