Final answer:
To prove ∠ 1 = ∠ 3, the relationship between ∠ KER and ∠ MEN must be established, which could be through similar triangles or parallel lines. A specific diagram or additional context is needed for a definitive proof.
Step-by-step explanation:
To prove that ∠ 1 = ∠ 3, we need more information from the question. However, based on the provided information about geometric congruence, we can deduce that when two angles are given to be equal (such as ∠ KER = ∠ MEN), they must be corresponding angles in similar triangles or alternate interior angles in parallel lines. If ∠ KER is equal to ∠ MEN due to either of these reasons, and if angles 1 and 3 are corresponding to these angles within a set of similar triangles or form alternate interior angles, then ∠ 1 would indeed be equal to ∠ 3. However, without a specific diagram or additional details, we cannot provide a definitive proof.