00:01
Okay, this gives us a diagram, the quadrilateral, and it talks about all these different things.
00:08
A, b, c, d are vertices.
00:10
E is a point on ad that makes a b equal to a, e, that's that part right there.
00:22
And then it says that b, e, c, is equal to c, d.
00:27
So that's this part here.
00:30
Says that b, e, c is 90 degrees, so it has a little box here.
00:35
A, d is parallel to b, c.
00:36
That's these little arrows here showing parallel lines.
00:40
D is equal to 2x, and b angle 1 is equal to x.
00:45
Whoever drew this picture is very rude.
00:49
They labeled angle b1 and angle b2 and angle e1, e2, and c1 and c2.
00:57
And that is just the root thing to do because it's really confusing.
01:01
You've got ones over here and over here and over there, and it looks like that they're saying that all the angles are the same, but they're not saying that.
01:09
I don't know why they drew it this way.
01:11
So if that was the root of your confusion, i totally understand.
01:15
So i'm just going to take my marker and mark through these because they're kind of dumb.
01:24
Sorry to say.
01:26
They're annoying.
01:27
They're very inconvenient and i'm sorry that they're there.
01:30
Okay, without those here, it's going to be a lot easier to navigate our way around.
01:36
So the first thing i noticed is that triangle a, b, e is an isosceles triangle as i saw.
01:54
Okay, i forgot as well.
01:56
That's because these are the same length, which means that this angle is equal to this angle.
02:01
So that'll be important to know.
02:04
Triangle e, d, c is also isosceles because of these pieces.
02:12
Here, which means that this base angle is equal to 2x, that base angle down there.
02:18
So that's also important to know.
02:21
Another thing i know is that since ad is parallel to bc, we see that right here, we know that whenever it is cut by this transversal, this angle that is on this line here is going to be equal to this angle down here.
02:44
So angle dec is equal to angle ecb, this one down here, because they're alternate interior angles.
03:00
That's a rule of parallel lines.
03:07
And then we also know, because of that same rule, i'll use a different color here.
03:12
Whenever this line cuts it, these two parallel lines right here, this piece is going to be parallel to this piece.
03:21
So we have that information now too.
03:25
So you'll notice i marked that because we already knew that these two angles were equal.
03:32
And then if we know that these two angles are equal, that means all three of them are equal.
03:36
And the same way over here, we knew that these were equal because i saw salis.
03:40
And then we just determined that these were equal by alternate interior, blah, la.
03:44
So all that information just tells us that all these pieces are equal.
03:48
So all that is going to come in handy as we are finding x.
03:56
If we know that all the angles have to add up to be 90 degrees, or sorry, all of the inner angles of a triangle need to add up to be 90 degrees.
04:15
So we know this, we're missing this piece over here...