 So section 4.4 is all dealing with triangle congruence proofs dealing with side side side and side angle side type of theorems So that's what we're going to work on. We're going to practice proving triangles are congruent using those two congruency theorems So every triangle congruence theorem proof is going to follow the same kind of general theme or the same general format We have three boxes and all of these three boxes together Lead us to the third box or sorry the fourth box. So these three boxes Let's call them box one two and three. They all funnel into box number four and here's why So all of these theorems. So for example, if we have side side side Then then we can prove that the triangles are congruent So what that means is we need to prove each pair of sides are congruent So we have in box one. This would be one pair of sides in box two and Also in box three we have a different pair of sides and what that allows us to do then is it allows us to prove That the triangles themselves are congruent. So it's a triangle something or other I don't know its name yet. We'll be congruent to triangle some other thing So that's why we're always going to have this three boxes kind of flowing into one So let's begin our first proof. Let's give it a shot. Oh, I forgot about one thing Sometimes there are things from diagrams or just how these pictures are drawn that we can consider as kind of given information So when we have two triangles that share a side then we can use that shared side in our proof. So for example triangle Side length AB and BA would be congruent to itself and then also we have the Sort of this bow tie type shape whenever we have two lines intersect then we create these vertical angles So in this case vertical angles one and two would be congruent and that doesn't need to be specifically given to us But it's sort of one of those pieces from the diagram. It can be assumed given to us Now we're ready to start some proofs