For the following right triangles:
AC≅DF
What else do we need to know to prove that the triangles are congruent by HL?
A. B. C. CB≅FE
D. AB≅DE

Let us first define Hypotenuse Leg (HL) congruence theorem:

If the hypotenuse and one leg of a right angle are congruent to the hypotenuse and one leg of the another triangle, then the triangles are congruent.

Given ACB and DFE are right triangles.

To prove ΔACB ≅ ΔDFE:

In ΔACB and ΔDFE,

AC ≅ DF (one side)

∠ACB ≅ ∠DFE (right angles)

AB ≅ DE (hypotenuse)

∴ ΔACB ≅ ΔDFE by HL theorem.

∠1≅∠2 by the alternate exterior angles theorem.

step-by-step explanation:

given, a ∥ b and ∠1 ≅ ∠3 .we have to prove that e ∥ f

we know that ∠1≅∠3 and that a || b because they are given. we see that by the alternate exterior angles theorem. therefore, ∠2≅∠3 by the transitive property. so, we can conclude that e || f by the converse alternate exterior angles theorem.

we have to fill the missing statement.

transitivity property states that if a = b and b = c, then a = c.

now, given ∠1≅∠3 and by transitivity property ∠2≅∠3 .

hence, to apply transitivity property one angle must be common which is not in result after applying this property which is ∠1.

the only options in which ∠1 is present are ∠1 and ∠2, ∠1 and ∠4

∠1 and ∠4 is not possible ∵ after applying transitivity we didn't get ∠4.

hence, the missing statement is ∠1≅∠2.

so, ∠1≅∠2 by the alternate exterior angles theorem.