Answer:
SAS postulate
Step-by-step explanation:
In the figure attached, quadrilateral ABCD is shown.
The Side Angle Side (SAS) postulate states that if two sides and the included angle of one triangle are congruent to two sides and the included angle of another triangle, then these two triangles are congruent.
AB is congruent to DC, and DB is the side common to triangles ABD and BCD. The included angle between sides AB and DB is angle ABD which is congruent with angle BDC, the angle included between sides DB and DC.
