Question: Identify the proof to show that $\triangle JKN \cong \triangle MKL$, where $K$ is the midpoint of $JM$ and $NL$, $\angle L \cong \angle N$, and $LM \cong JN$
1. **State the problem:** We need to prove that $\triangle JKN \cong \triangle MKL$ given that $K$ is the midpoint of $JM$ and $NL$, $\angle L \cong \angle N$, and $LM \cong JN$.
2. **Given information:**
- $K$ is the midpoint of $JM$ and $NL$, so $JK = KM$ and $NK = KL$.
- $\angle L \cong \angle N$ (given).
- $LM \cong JN$ (given).
3. **Goal:** Prove $\triangle JKN \cong \triangle MKL$.
4. **Use the Midpoint Theorem:** Since $K$ is the midpoint of $JM$, we have
$$JK = KM$$
Similarly, since $K$ is the midpoint of $NL$, we have
$$NK = KL$$
5. **Identify corresponding parts:**
- Side $JK$ corresponds to side $KM$.
- Side $NK$ corresponds to side $KL$.
- Angle $\angle N$ corresponds to angle $\angle L$ (given congruent).
6. **Check the congruence criteria:**
We have two pairs of sides equal ($JK = KM$ and $NK = KL$) and the included angles $\angle N \cong \angle L$.
7. **Apply SAS (Side-Angle-Side) Congruence Postulate:**
Since two sides and the included angle of $\triangle JKN$ are congruent to two sides and the included angle of $\triangle MKL$, we conclude
$$\triangle JKN \cong \triangle MKL$$
**Final answer:** $\triangle JKN \cong \triangle MKL$ by SAS congruence postulate.