Introduction to Euclidean geometry
Lines, Line Segments, and Rays Difference between lines, line segments, and rays
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line, but why we call it a segment is that it actually has a starting and a stopping point. So most of
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- What I want to do in this video is think about the difference between a line segment (a line segment)
- a line (a line), and a ray (and a ray). And this is kind of the pure geometrical versions of these, of
- these, things. And so a line segment is actually probably what most of us associate with a line in our
- everyday lives. So a line segment is something just like that (for a lack of a better word) a straight
- line, but why we call it a segment is that it actually has a starting and a stopping point. So most of
- the lines we experience in our everyday reality are actually line segments when we think of it from a
- pure geometrical point of view. And i know i drew a little bit of a curve here, but this is supposed
- to be completely straight. But this is a line segment. The segment, the segment is based on the fact
- that it has an ending point and a starting point, or a starting point and an ending point. A line if
- you're thinking about it in the pure geometric sense of a line, is, essentially, it does not stop. It
- doesn't have a starting point and an ending point. It keeps going on forever in both directions so a
- line would look like this (a line, would look like this) and to show that it keeps on going on forever in
- that direction right over there we draw this arrow, and to keep showing that it goes on forever in kind
- of the down left direction, we draw this arrow right over here. So obviously, y-you no I've never encountered
- something that just keeps on going straight forever (forever), but in math (thats the neat thing about math) we
- can think about these abstract notions and so the mathematical purest geometric sense of a line is the
- straight thing that goes on forever. Now a ray is something in between. A ray has a well defined starting
- point (so that's its starting point), but then it just keeps on going on forever. So then, so the ray
- might start over here, but then it just keeps on going (then it just keeps on going). So that right over
- there is a ray. Now that out of the way, let's actually try to do the Khan Academy module on recognizing
- the difference between line segments, lines and rays. And i think you'll find it pretty straight forward
- based on, on our little classification right over here. So let me get the module, let me get the module
- going. (let me, where did i put it? where did i put it? there you go!) Alright, so what is this thing
- right over here? Well it has two arrows on both ends, so it's implying that it goes on forever. So this
- is going to be a line. (lets check our answer.) Yeah! Its a line. (now it's taking some time, oh correct,
- next question) Alright now what about this thing? Wait once again arrows on both sides means that this
- thing is going to go on forever in both directions, so once again it is a line. Fair enough, lets do
- another one. Here, we have one arrow, so it goes on forever in this direction, but it has a well defined
- starting point. So it starts there and then goes on forever. And if you remember that's what a ray is.
- One staring point but goes on forever. So it goes, or more when you think about it, it goes on forever
- in only one direction. So that is a ray. So lets do another question. This right over here, you have
- a starting point and an ending point. Or u can call this the start point and the ending point but it
- doesn't go on forever in either direction. so this right over here, is a line segment. (there you go)
- So hopefully that, that gives you enough t-t-to work your way through this module. And you might notice that
- when i did this (when i did this) module right here, there is no video and that's exactly what this video
would an infinite line and an infinite ray be equally long? That's my question.
Magnus
Yes. It's a tricky concept because it feels like an infinitely long ray is only half as long as an infinitely long line. But technically, half of infinity is still infinity.
nickspoon
maxig7
Gabe
Residuum
MelDee.24
Anya
Reed Lindsey
hmccosh
Mark Waterhouse
what would you use this for in real life?
if you deal with architecture or any type of designwork geometry even the basics like this are crucial
ldmurphy
So then what is the point of infinite ray and infinite line?
A ray begins at a point and then continues on in one direction like the rays of the sun. An infinite line goes off in both directions. It has no beginning and no ending.... much like a highway has many points you can stop along the way but seems to continue on and on in both directions.
ROBERTSTEVENSON2015
What is the difference of a ray line segment and a line?
A line segment connects two points and stops at those two points.
A ray starts at a point and continues forever in one direction.
A line continues forever in both directions.
A ray starts at a point and continues forever in one direction.
A line continues forever in both directions.
Katharine
At 2:54 if it didn't have the point would it be considered a ray?
Only if x=5(6/7)+y
what is the difference between a ray segment and a line?
Michael pignatari
A ray segment is when you have a defined starting and you go off in any direction and then have a defined stopping point.A line has no defined starting and no defined ending,so it goes on forever.I hope this helps!
Simran
What is a segment?
A segment(when talking about a line) is only part of a line. Like he said, a line goes on forever but a line segment doesn't. ♥
math41
would an infinite line and an infinite ray be equally long?
No. A line will always be longer than a ray. A ray has a point that starts it. A line keeps going either way! :) hope this helps! :)
Is there any kind of palpable object on Earth that has the same properties as a ray?
These lines are abstractions since no object on earth is a line with an infinite length, however, perhaps if you shine a laser pointer (or perhaps a more powerful laser to get the point across) into the night sky, the light comes out like a ray since it has a finite start on one end and continues into the sky and into space and you can't see where it ends.
if a a ray is infinte but with a starting point does it never come back onto itself? essntialy then turning itself into a line?
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