So how do we prove it?

So how do we prove it?First, I'll write down what we know.We know that point M is the midpoint of AB.We also know that sides AC and BC are already congruent.Now let's see. What does the midpoint tell us?Luckily, I know the definition of midpoint.It is basically the point in the middle.What this means is that AM and BM are the same length,since M is the exact middle of AB.In other words, the bottom side of each of our triangles are congruent.I'll put that as step two.Great! So far I have two pairs of sides that are congruent.The last one is easy.The third side of the left triangle is CM, and the third side of the right triangle is -well, also CM.They share the same side.Of course it's congruent to itself!This is called the reflexive property.