Triangle abc is congruent to a'bc' by the hl theorem. what single rigid transformation maps abc onto a'bc'? dilation reflection rotation translation

HL theorem or hypotenuse leg theorem states if the hypotenuse and one leg of a right triangle are congruent to the hypotenuse and one leg of another right triangle, then the triangles are congruent. Now by above definition if the triangles are having a same leg then they would together also form a triangle so if we imagine the common leg as a mirror we can see both are reflection of each other so if the reflection transformation of one triangle is done it completely maps on second