Mentor: Please draw the coordinate axis on your paper. Now label the x and y-axis. Now label each line on the x and y axis with a scale of one.
Mentor: Did you know that the coordinate axis is a plane? Student: No. What is a plane? Mentor: A plane is a flat surface that continues out infinitely. The best way to see what a plane is like is to imagine a piece of paper that never ends. Student: So does infinity mean never ending? Mentor: Infinity is the biggest number that there is. So a plane stretches out to a point that is so far away we say it never ends. Student: So a plane stretches out to the end of the universe. Mentor: Yes, it stretches to the end of the universe and much farther. Now, can any one remember what a line is? Student: A line is made up of at least two points that are on a straight path. Mentor: Yes, very good. Let's draw one.
Mentor: Now, does anyone have an idea of what a ray is? Student: The beam of light that comes out of a ray gun. Mentor: Good idea. A ray gun has a starting point and it goes on forever if it never hits its target. A ray starts at one point and it continues out to infinity. Mentor: Let's draw a ray.
Student: So, what is the difference between a line and a ray? Mentor: A line goes on to infinity in both directions, but a ray stops on one end. If you cut a line in half, you make two rays. Now, can anyone guess what a line segment is? Student: Is it a line with two ends? Mentor: Exactly right. A line segment is part of a line that has two endpoints. Let's draw one on paper.
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