Line of reflection example

We're asked to draw the line of reflection that reflects triangle ABC, so that's this blue triangle onto triangle A'B'C', which is this red triangle right over here. They give us a little line drawing tool in order to draw the line of reflection.

So the way I'm going to think about it is, when I just eyeball it, they look, it looks like I'm just flipped over some type of a horizontal line here. But let's see if we can actually construct a horizontal line where it does actually look like the line of reflection.

So let's see C and C' how far apart are they from each other? So if we go 1, 2, 3, 4, 5, 6 down, so they are 6 apart. So let's see if we just put this 3 above C' and 3 below C. Let's see if this horizontal line works as a line of reflection.

So C or C' is definitely the reflection of C across this line. C is exactly 3 units above it and C' is exactly 3 units below it. Let's see if it works for A and A'. A is one, two, three, four, five units above it. A' is one, two, three, four, five units below it, so that's looking good.

Now let's just check out B. So B we can see it's at the y-coordinate here is seven. This line right over here is y is equal to one. And so what we would have here is, let's see, this looks like it's six units above this line and B' is six units below the line. So this indeed works. We've just constructed the line of reflection that reflects the blue triangle ABC onto triangle A'B'C'.