The diagram shows that FG = IJ are congruent segments due to the double tickmarks. These are the hypotenuses of the right triangles.
So that takes care of the "H" in "HL".
The L stands for "leg", so we need to have a congruent pair of corresponding legs.
Due to the orientation of the triangles, it's not clear how the corresponding legs match up, but if any of the following is true
- EF = IK
- EF = JK
- EG = IK
- EG = JK
then we'd have enough to use HL.
