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## 4th grade

Drawing parallel line segments

Sal draws parallel line segments with given points. Created by Sal Khan.

## Want to join the conversation?

- When does a line truly end? When it goes off the paper?(12 votes)
- Lines never end unless they are line segments or rays, which are different from lines. Line segments end from both ends while rays continue from one end forever.(10 votes)

- why does math exist?(12 votes)
- why does every time that i see a question it says IF YOU UPVOTE YOU WILL WIN 1,000 DOLLARS SO PLS UPVOTE ME PLS JUST UPVOTE ME(8 votes)
- How do you get the next Aqualine avatar? And what qualifies as mastering a math skill? Do you have to watch all the videos for it to count?(5 votes)
- I got mine by mastering the exercises. A skill is mastered by earning the crown on top.(5 votes)

- I heard that two parallel lines intercepts itselves in the infinity. Is that true? Why?(3 votes)
- As mentioned by Robin, if they are parallel lines then they would never intercept at any point. They share the same slope or rise/run.(5 votes)

- is it fun making videos(6 votes)
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- i don’t get when you say like two endpoints and like zero direction.(4 votes)
- It means that it ends with two points,and zero direction means that it goes for infinity. Right?(4 votes)

- how I can imagine that a line which is not in the axis direction but cover the path of both axes(5 votes)
- I might have missed it in one of the videos, but how do I draw a parallel line using an oblique line and a compass? I didn’t understand my teacher when she went over it. Thanks!!(5 votes)
- The whole point is that parallel lines never meet, they are straight and go for infinity(4 votes)

## Video transcript

Any pair of points can be connected by a line segment. That’s right. Connect two pairs of black points in a way that creates two parallel line segments. So let’s see if we can do that. So I could create one segment that connects this point to this point and then another one that connects this point to this point. And they look pretty parallel. In fact, I think this is the right answer. If we did it another way, if we had connected that point to that point and this point to this point, then it wouldn’t look so parallel. These clearly, if they were to keep going, they would intersect at some point. So let me set it back up the way I did it the first time. Let me make these two points parallel. And these are line segments because they have two end points. They each have two end points. And they continue forever. Well they don’t continue forever. They continue forever in no directions, in zero directions. If it was a ray, it would continue forever in one direction. If it’s a line, it continues forever past both of these points. In fact, it wouldn’t have end points because it would just continue forever in both of these directions. Let’s do one more. Drag the ray so it has an endpoint at A, so we want to make its endpoint at A where the ray terminates and goes through one of the other black points. The ray should also be parallel to the pink line. So I have two options. I could make it go through this black point, but it’s clearly not parallel. In fact, it looks perpendicular here. So let’s try to make it go through this point. Well, yes, when I do that, it does indeed look like my ray is parallel to the pink line. And this is a ray because it has one endpoint. This is where the ray terminates. It’s an endpoint. It literally ends there. And it continues forever in one direction. In this case, the direction is to the right. It continues forever to the right. So it continues forever in one– continues forever in one direction.