It is the AAS Postulate.
Explanation: You’re given two right angles (because perpendicular sides make right angles).
This also means that the angle next to them are also right angles, because they are linear pairs (180-90=90)
The right angles are:
This is your first A.
Both triangles also share a similar angle:
This is your second A.
You’re given side BD is congruent to EC.
This is your S.
It’s AAS and not ASA because the order refers to how they are connected: they are congruent in the order that the first set of congruent angles connect to the next, then to the congruent side.
