 another session on problem solving on congruent triangles. In the given question, AB is equal to CF. So, where is AB? Let's locate AB. So, this is A, this is B. So, AB is and AFE is congruent to angle AFE. Angle AFE, where is AFE? Let's say, is equal to CBD. Okay, we have to prove that triangle AFE is congruent to CBD, CBD. Okay, so let's start with whatever is given. So, if you see what is given guys, we have been given that AB, this diagram is equal to, we have seen that in the diagram also and we have to prove CBD, CBD. That means angle A will be equal to angle C. Angle F is equal to angle B. So, in such questions what we need to do is, assume that this is true. Whatever is the demand of the question, assume that that is true and then calculate backwards and see whether you arrive at B. So, if AFE and CBD were to be congruent, then what do we need to see or prove? See, and one angle is also given. So, is this angle equal? Yes, it's already given. And is EF, the other, the two arms of that angle must be equal. So, is EF equal to BD? Yes, EF is equal to BD, it's already given. And is AF is equal to CB? Now, here is, this is not direct, right? So, AF is CB, we have to prove it. But how do we prove it? What is given? It's given that AB is equal to CA, right? Now, if we add BF to both AB as well as CF, then what will happen? Let's see. That is quite indicative of our, you know, direction. So, hence, prove. What I'm going to do is, CBA is equal to, or AB is equal to CF given. AB is equal to CF, it's given. Okay? Now, if I add AB plus BF, I'm adding BF to both. And BF plus CF, right? I can add the same thing to both sides of an equation. So, what is AB plus BF? Check. AB plus BF is AF. So, AF is equal to, what is BF plus CF? Again, this is, right? So, AF is BF. And this is what we wanted and we have got it. Okay? So, now you will say, in triangle, it's to triangle AFE, whichever is given. So, AFE triangle, which one? CBD. We have got first criteria, AF is equal to CF, right? From here. Sorry, AF is equal to, not CF. AF is equal to CB. From here. Okay? Now, AF is equal to CB and already what is given? It's given that AFE is equal to, already given. Where is it given? Here. And third, EF, that means by SAS, SAS Congruence Criterion. By SAS Congruence Criterion, these two triangles are congruent. Which two triangles AFE? Please be careful while writing the order of the points. So, AFE is, that's what I was saying. So, A is corresponding to, A will correspond to C, right? So, C and then F is corresponding to B. Proof is clear. So, again we use SAS Congruence Criterion to prove this.