1 00:00:01,139 --> 00:00:10,140 Let's practice drawing angles. We have to be familiar with our protractor to do this. 2 00:00:10,140 --> 00:00:17,140 The first angle I'm asked to draw is 50 degrees. I need to start by giving myself a straight line to draw from. 3 00:00:17,140 --> 00:00:26,140 Now that I have the straight line, I can zero my protractor using this dot on one end of the straight line that I drew. 4 00:00:26,140 --> 00:00:32,439 And then, counting up from zero, which means this time I'm using the inner numbers on the protractor, 5 00:00:32,659 --> 00:00:43,079 I go up to 50, and I put a line there that shows a 50 degree angle with the line that I already drew. 6 00:00:44,060 --> 00:00:46,679 It is that easy to draw a 50 degree angle. 7 00:00:47,380 --> 00:00:53,299 Let's try drawing a 90 degree angle, but we will use the left side of the protractor this time instead. 8 00:00:53,299 --> 00:00:54,659 I need a straight line. 9 00:00:54,659 --> 00:00:58,659 Once I have my straight line, I can zero the protractor on it. 10 00:00:58,659 --> 00:01:02,659 And because I'm on the left side of the protractor, and I know I have to count up from zero, 11 00:01:02,659 --> 00:01:05,659 this time I need to use the outer set of numbers. 12 00:01:05,659 --> 00:01:09,659 I follow those numbers until I get to 90, and I put a dot. 13 00:01:09,659 --> 00:01:14,659 And then I draw a line between that dot and the vertex I started from, 14 00:01:14,659 --> 00:01:17,659 and I have created a 90 degree angle. 15 00:01:17,659 --> 00:01:22,099 Some angles you're asked to draw are bigger than 90, though. 16 00:01:22,099 --> 00:01:23,099 What do you do? 17 00:01:23,459 --> 00:01:25,519 Well, start with a straight line. 18 00:01:28,959 --> 00:01:33,959 Put your vertex of your protractor, the 0 dot, on the vertex at one end of the line. 19 00:01:37,170 --> 00:01:38,829 And then we're counting up from 0. 20 00:01:39,629 --> 00:01:41,810 Well, that's the inner numbers on this side of the protractor. 21 00:01:41,810 --> 00:01:47,329 So I keep on going past 90 until I get 214, which is going to be right about here. 22 00:01:48,829 --> 00:01:53,109 And then I draw a line between the dot that I marked and the vertex that I was using. 23 00:01:54,370 --> 00:01:56,549 This is a 114 degree angle. 24 00:01:57,129 --> 00:02:02,750 A 180 degree angle is also known as a straight angle. 25 00:02:02,750 --> 00:02:12,159 If you have a line, you zero your protractor, and counting up from zero, meaning using the 26 00:02:12,159 --> 00:02:16,120 inner numbers this time, I go all the way to 180 while it's straight over here. 27 00:02:16,120 --> 00:02:20,639 All I'm doing when I connect them, the vertex to that dot, is I'm continuing the straight 28 00:02:20,639 --> 00:02:22,080 line I started with. 29 00:02:22,080 --> 00:02:28,490 So this is a straight angle, or a 180 degree angle. 30 00:02:28,490 --> 00:02:34,930 What gets a little bit tricky is that the protractor's numbers only go to 180 and then 31 00:02:34,930 --> 00:02:36,550 they stop. 32 00:02:36,550 --> 00:02:40,370 But some angles you may be asked to draw are bigger than 180. 33 00:02:40,370 --> 00:02:52,490 In order to draw this 230 degree angle, you have to know that the angle of a circle is 34 00:02:52,490 --> 00:02:55,409 360 degrees. 35 00:02:55,409 --> 00:03:03,129 So what we can do is we can say 360 degrees minus 230 is equal to 130. 36 00:03:03,129 --> 00:03:10,330 Let's try drawing a 130 degree angle underneath our starting line. 37 00:03:10,330 --> 00:03:13,729 Counting from zero, 130 is over here. 38 00:03:13,729 --> 00:03:24,349 I put a dot, I draw a line connecting my vertex to that dot, but the 130 degree angle is this 39 00:03:24,349 --> 00:03:30,590 smaller one here. I was asked for the 230, which is complementary to the 130. 230 is 40 00:03:30,590 --> 00:03:36,270 what I get if I subtract 130 from the circle. So therefore, all I have to do is put this 41 00:03:36,270 --> 00:03:43,229 symbol for the angle on the other side, and I must have a 230 degree angle. Let's try 42 00:03:43,229 --> 00:03:49,430 the same trick with the 335 degree angle. There's my starting line. I zero my protractor 43 00:03:49,430 --> 00:03:56,430 on it. I can't go up to 335, that's far bigger than the 180 I have in my protractor. So I 44 00:03:56,490 --> 00:04:03,490 do the circle, 360, I subtract 335, and my answer is 25. What I'm going to do is I'm 45 00:04:03,870 --> 00:04:11,520 going to draw a 25 degree angle instead, and then instead of putting the symbol for the 46 00:04:11,520 --> 00:04:17,220 angle on the inside, which is a 25 degree angle I know, I put it on the outside. And 47 00:04:17,220 --> 00:04:24,819 That must be a 335-degree angle because 25 plus 335 is equal to the 360-degree circle.