S A S congruence rule: Two triangles are congruent if two sides and the included angle of one triangle are equal to the two sides and the included angle of other triangle.
If two triangles are congruent by SAS, and the angle is 90, then by CPCT{corresponding part of congruent triangle) the hypotenuse of the two triangles will be congruent.
Now, as hypotenuse and one leg are congruent in both triangles, we can apply RHS congruent
