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In Geometry, we have actually several undefined terms: **point, line and plane**. Indigenous these 3 undefined terms, all other terms in Geometry have the right to be defined. In Geometry, we specify a point as a location and no size. A heat is identified as something that extends infinitely in one of two people direction however has no width and is one dimensional while a aircraft extends infinitely in 2 dimensions.

There space three undefined state in geometry. From these terms we specify everything else. The very first term is point. The 2nd term is plane. And the third undefined term is the line. For this reason let's go ago and specify these as much as us can. Now we're no really specifying point, we're just describing it. A point has no size; it only has actually a location. And also the method that we label it is through a funding letter. So we can call this suggest P. A aircraft is a level surface that has no thickness, and it will extend infinitely in every direction.So one means to visualize what a airplane could be is to think about a sheet of paper. Or if there room two differences in between a paper of paper and a plane, the very first is this document does not prolong in every direction. Secondly, this paper actually has actually some thickness and also a aircraft will not. Now you deserve to name a aircraft using a single capital letter, generally written in cursive, or by 3 non-collinear points. And collinear we'll talk about in a 2nd here, however collinear means they're no on the exact same line. For this reason let's speak you had a point right here: suggest A, allude B, and point C. Friend could contact this plane, plane ABC. Definition of coplanar: We in reality can specify this, is points, lines, or anything, segments, polygon in the exact same plane. So two things space coplanar if they are, as with we have actually in the photo here, in the very same plane. Therefore "co", you deserve to think of it together a word for sharing. So you can think the coplanar together sharing the very same plane. Now the third undefined hatchet is a line. And a line is collection of clues or, words that you might learn later on is locus, expanding in either direction infinitely. Therefore a line is going to be all the points, and we have the right to actually choose two of castle to name it. So we can call this heat AB. Currently when you're labeling a line, it's crucial to encompass at least two points. Or if you have some kind of smaller sized letter end here, us can call this heat L. But notification how I'm writing the arrows over my letters; I have arrows on either side. And these arrows call you, the geometry student, that it expand infinitely in this direction. Now this arrow here extend infinitely in that direction. You can have points be collinear, the is, they share the very same line. So right here we might have, C, D, and E space all collinear. And also if friend look at allude F here, I attracted this in to draw a contrast. You have the right to see that point F is not on this line, therefore F is no collinear v C, D, and also E. Yet I could say the E is collinear v C and also D, D is collinear through C and also E, and C is collinear through D and E.

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Therefore the three vital terms that room not definable, yet only describable, are the line, which is a collection of points expanding infinitely in one or the other direction; plane, i m sorry is a flat surface v no thickness; and the 3rd undefined ax is suggest and that has a location and also no size.