Project Math Access DVD 05 - Geometry - Part 08 Transcript Start Audio Description: Part eight; Using a braille compass and a braille straight edge to construct line segments. TEACHER: Alright John, we just got this worksheet from your math teacher on constructions, and I’m going to quickly... braille up the lines and then have you construct what you need to construct using the compass. [sound of braillewriter] TEACHER: So I’m just going to make-- Audio Description: The teacher shows the original problem to the camera. TEACHER: this line AB using the braillewriter, putting a full cell at the start and... then doing dots 2-4 going across and then a full cell again and then labeling it with the A and the B. Audio Description: The teacher puts down the original problem and returns to the braillewriter. [sound of braillewriter] Audio Description: The teacher now labels the line she just created on the braillewriter. The teacher makes a correction on the sheet in the braillewriter. The teacher takes the sheet out of the braillewriter and hands it to the student John. TEACHER: Okay, so here is the diagram for number 1 and I will read you the directions. It says, “Construct each of the following using a straight edge and a compass. Do not erase any of your marks. Audio Description: John checks the problem on the braille sheet. TEACHER: Number 1, given line AB, construct line segment CD, such that CD equals 3AB. JOHN: CD equals 3AB. Okay, so first of all, I need the ruler. Audio Description: The teacher hands the ruler to John. It is a thick plastic ruler with a metal guide. TEACHER: Let me get you the ruler. And here's your ruler. JOHN: Thank you. TEACHER: And I also gave you the cardboard to do it on so that... Audio Description: John places the ruler on the line, in order to measure it. JOHN: I'll put it right there, see how long AB is... let's see, maybe 3 inches. No, wait, that's not quite right. Ah, it's pretty close. It looks like it's about 2 1/4 inches long. You can see where the ruler is and you can see where the line is. Okay, so approximately then, if it's about 3, I want this... Audio Description: John grabs the compass. JOHN: to be about 9 inches. Audio Description: John adjusts the compass to increase the radius. So I'll just mess around with this thing until I think it's far enough apart, and then I'll measure it. Audio Description: John continues to adjust the compass. TEACHER: Okay, how can you do it if the compass isn't going to get out to 9 inches? JOHN: I think it will actually. Because we're already at, let's see, where are we? We're already at 3, aren't we? Audio Description: John measures the opening of the compass with the ruler. JOHN: 3 and it's... TEACHER: I don't believe the compass is going to get out to 9, so since they want 3AB... So, what can you do with the compass, to make it, so that you can get 3 ABs? JOHN: 3 ABs, well, I'm just thinking, it's been awhile since I've done this, but if you put... it at one point and then you draw a line that goes down, like let's say you put it here. You draw a line that goes down and then you move it over and then you draw a line this way. Audio Description: John draws a partial circle with the compass, moves it two inches, then draws another partial circle. JOHN: No. TEACHER: You're on the right track. What you're going to do is you're going to measure line AB with your compass, and then you're going to move it over 3 times... so that you have 3, use the compass 3 times to make it so that you're getting the 3AB. JOHN: Yeah, okay, Audio Description: John puts the compass on the line segment AB. JOHN: oh so I didn't need the ruler I guess. Oh well. TEACHER: Make sure that when you're constructing your lines with the compass... that you're doing it on the cardboard and not on the table. JOHN: No, I know, I'm just putting it down so I can see... Okay, so this looks about the right, well, maybe even just a little more narrow. Audio Description: The opening of the compass is very close to the length of the line. JOHN: Right about there, that looks about right. TEACHER: Okay. Audio Description: John closes the compass slightly. JOHN: Okay, so, alright now I'll do it on the cardboard. Audio Description: John turns the paper over. JOHN: Alright, now I want to put it at the end of line AB Audio Description: John searches for line AB. JOHN: I think. So that's right about here, I think I'll start. Audio Description: John accidentally puts the compass point at the beginning of line AB. TEACHER: Okay, wait a second, you want it to be 3 times AB. Right now you're at the beginning of where line AB starts. JOHN: Okay. TEACHER: So you need to move to where the end of AB is. Audio Description: John locates the correct point on the line. JOHN: Okay, there we go. That's about right. TEACHER: And you want to try to make your mark with your compass on the same line as AB is going. JOHN: So that would be like right here. TEACHER: Correct. JOHN: And I would just want to make a mark, well it's going to curve a little bit but... Audio Description: John creates a semicircle with the compass, directly to the left of the line. JOHN: okay-- TEACHER: Okay. JOHN: Okay, that's good. TEACHER: Now you did one so what are you going to do with... JOHN: Now I think I have to move over to this right here. Audio Description: John moves the compass to a random point on the semicircle. TEACHER: Okay, now this is where your straight edge is going to come into effect, because now you've moved up towards the top... so you want to use your straight edge so that you're drawing these along the same line. JOHN: Okay, this is how the other... so where's the straight edge? Audio Description: John takes the ruler, places is on the line and extends it toward the semicircle. JOHN: Let's see, where was that line? That line was right here. I'm just going to move my compass. That line was right here and this one is right here, so that looks pretty good. Audio Description: John does not have the ruler parallel to the line. TEACHER: Okay, just so that you can feel that you're going up on an angle, so you to try to make it so that it's going straight. Audio Description: John gets the ruler parallel. TEACHER: So now find where you made the curve with the compass and where the straight edge... meet and that's where you're going to put the center of your compass again. JOHN: Okay, so actually, I'm going to move this, well I know they meet right here. But if I put my center right there, it's going to make the line go down a little bit. TEACHER: No. Audio Description: John has his finger on the point where the straight edge intersects the semicircle. JOHN: Okay. TEACHER: So mark it with, I'll move your straight edge away. Audio Description: John places the sharp end of the compass at the point indicated by his finger. JOHN: Okay. TEACHER: And then which way are you going to make your... JOHN: I'm going to make it this way. TEACHER: Towards the left? Audio Description: John creates a new semicircle to the left of the point. JOHN: Yes. Oops. [sound of line being drawn] JOHN: Okay, that's good. That's good. Audio Description: We now jump to a point after John has created the next line. TEACHER: Okay John, do you want to check to see what you have so far? JOHN: Yes, now I've drawn those two lines, so that CD is going to be 3AB. TEACHER: Okay, here's a Wikki Stix, if you want to mark it with a Wikki Stix and then I will mark it with a pencil. JOHN: Okay, line, well it starts here. It's going over the original line of AB and now all I want to do is make sure that I'm going straight across and then I'll mark C and D. TEACHER: Okay, and where does your line end? JOHN: It ends right, well, it ends right here actually. TEACHER: Okay. JOHN: Ends a little bit after this Wikki Stix. I also should probably use a straight edge to make sure that I didn't curve on my line with the Wikki Stix, Audio Description: John uses the ruler to check the straightness of the Wikki Stix. JOHN: because I know this part of it is... straight. This is straight here, oh yeah, see I did. I need to move it just a little bit. TEACHER: Nice job checking. JOHN: Yeah, is should be right there. Actually my guard got in the way, but that's okay. Now if l put the end down, it's better. TEACHER: Okay, now I will mark that this is question number 1 for you in ink and then I will draw the line with the pencil, as the... Wikki Stixs sometimes fall off when... you hand them in. So now what am I going to label this newline? JOHN: This newline would be line CD. TEACHER: Okay, so C is going to go where? Audio Description: John searches for point C. JOHN: Okay, first of all, these are points A and B. C is going to go right here... and D is going to go right here. TEACHER: Okay, you've got D right because it's going to be the end of our line, but not C. JOHN: Oh no, C is going to be here. TEACHER: Good job. Audio Description: C is at the beginning of the line, the same point as A. TEACHER: Okay, so I'll label that C and label that D. Nice job.