This is a transversal line.

You have a transversal, parallel lines

So that right there is the transversal.

And then let me draw a transversal here. So let me draw a transversal. This is also a line.

lines, then this segment up here is a transversal.

This is a transversal, these two lines are parallel

So, in the first time we view this as the transversal AC is a transversal of AB and CD which are parallel lines

So, first of all we view this as a transversal

We view AC as a transversal of AB and CD

So if that is a transversal, what do you know about transversals?

CAE must be congruent to BDE And now we have a transversal

Now AB is a transversal and BD and AC are the parallel lines

And this line that intersects both of this paralel lines we call that a transversal.

They're between the two lines but they're all on the opposite sides of the transversal.

Then this is clearly a transversal of those two parallel lines. This is clearly a trasnversal.

This is alternate interior angles are congruent when you have a transversal intersecting two parallel lines

The angles that are formed at intersection between this transversal line and the two paralel lines.

And so if you have a transversal, the corresponding angles are congruent, you're dealing with parallel lines.

Came to understand, there's a set of core competences every young person must be well on the way to mastery before he or she finishes high school.

So, we know that AB is parallel to CD by alternate interior angles of transversal intersecting parallel lines

ADB for the exact same reason, they are alternate interior angles of a transversal intersecting these two parallel lines

If we look at diagonal AC or we should call it transversal AC we can make the same argument

Well, the first thing that we might realize is that, look, corresponding angles are equivalent. This angle, the angle between this parallel line and the transversal, is going to be the same as the angle between this parallel line and the transversal.

So if I just extended it like that, you see it's a transversal, and I could go the other direction as well.

So, we know that angle ABE must be congruent to angle CDE by alternate interior angles of a transversal intersecting parallel line

So if I extended that line like that, and if I extended this line like that, then segment AD is just a transversal.

And so if this angle right over here is 4x, it has a corresponding angle where the transversal intersects the other parallel line.

So, if we look, view DB, this diagonal DB, we can view it as a transversal for the parallel lines AB and DC

And now we have this kind of transversal of these two lines that could be parallel if the alternate interior angles are congruent

And then we change our thinking a little bit and we view AC and BD as the parallel line and AB as the transversal

Because they're corresponding angles, and you could see that by inspection, and if you moved around the transversal, it would make sense that that's the case.

And this diagonal, depending on how you view it is intersecting two sets of parallel lines so you can also consider it to be a transversal

This angle that's kind of right below this parallel line with the transversal, the bottom left, I guess you could say, corresponds to this bottom left angle right over here.

Now you can also view this diagonal DB, you can view this as a transversal of these two parallel lines, of the other two pair of parallel lines, AD and BC

Half of the..or maybe most of the work on all these is to try to see the parallel lines and see the transversal and see the things that might be useful for you.

Well, once again these could be alternate interior angles, they look like they could be, this is a transversal and here's two lines here which we're not sure they're parallel but because the alternate interior angles are congruent we know that they are parallel

Now, if we kinda change our thinking a little bit and instead we now view BD and AC as the parallel line and now view AB as the transversal, then we see that angle EBD is going to be congruent to angle BAC because they're corresponding angles

And if i drew parallel lines, maybe I'll draw it straight left and right, it might be a little bit ore obvious so if I assume that these two lines are parallel and I have a transversal here what I'm saying is this angle is going to be the exact same measure as that angle there.