How to identify Points, Segments, Lines and Rays.

Question

I'm lost! I need to know how to explain this to my daughter 

Answer 1

Hi Ervin,

Since the question doesn't specify much more than "how to identify" I might not cover exactly what your daughter needs; if the following isn't enough feel free to follow up with a more detailed question. In short however:

 

A point is basically the geometric figure corresponding to what we think of as a "dot" in the real world, with the key aspect that the geometric point will have no length, no width, and no height/depth, while a "dot" we make with even a very sharp pencil will have some dimension. So the geometric figure is an "ideal" shape not found in that exact form in the real world, but which is captured by the notion of a "dot".

Similarly, a segment (sometimes called a Line Segment in contrast to a full Line, described below) is the "ideal" geometric figure represented by a straight segment you might draw a pencil and a ruler. Straight means no "turning" or bending, and "segment" means it starts at one point and ends at another. The ideal geometric figure has length but no width or depth, while the one we draw with a pencil has a (very very thin) width even if we use a very sharp pencil.

A Line is what you get when you start with a Segment (or Line Segment) but let it continue indefinitely, forever, in each of the two opposite directions (say one going North forever and the other heading South forever), so there are no longer any endpoints. We can't draw "forever" with a pencil so we use an "arrowhead" on each side of the drawn line to indicate "continue forever in this direction". A ray is like a line except we start with a Line Segment and we keep one end point out of the two, and do the "extend forever" in only one direction. Like an endpoint is a starting place for the ray, which then continues in a straight direction (say North) forever and ever.

P.S. look at your computer keyboard. If it's like mine, you'll have an "up arrow" and "down arrow" and "left arrow" and "right arrow" Those are depictions of four rays! If you have followups just ask here. Hope this helps!