Its HL Theorem HL Theorem is a theorem to prove the congruence of two right triangles. Two right-angled triangles are congruent (abbreviated as HL) if their hypotenuses correspond to a right-angled side.

1, HL theorem is used on the premise that one of the two right-angled triangles is equal to the hypotenuse. It is not true in any triangle. When judging the congruence of two right-angled triangles, the method of judging any triangle can still be used.

2. Two right-angled triangles (Rt triangles) with equal hypotenuses and one right-angled side are congruent (abbreviated as "HL"), and these two triangles are called "(right-angled) congruent triangles".

3. Scope of application: prove that two right triangles are congruent.