Answer:
the HL Postulate
Explanation:
The diagram gives us the information that 2 sides and 1 angle are congruent. Since the sides we know are a leg and the hypotenuse, and it is a right angle- we know to use the HL (Hypotenuse-Leg) Postulate.
If the angle given was the angle between the hypotenuse and the leg, we could use the SAS (Side-Angle-Side) Postulate. But, since it is the right angle instead- we know to use the HL Postulate!