1 00:00:00,610 --> 00:00:07,240 In this video, let's discuss some more basic terms related to a polygon, so we take our Pentagon as 2 00:00:07,240 --> 00:00:07,950 an example. 3 00:00:08,260 --> 00:00:11,810 Let's name the corners as ABCDE. 4 00:00:12,400 --> 00:00:17,760 Now, the sides of the polygon are these nine segments, right? 5 00:00:17,890 --> 00:00:20,010 So we have five line segments. 6 00:00:20,020 --> 00:00:22,450 ABC could be. 7 00:00:22,450 --> 00:00:26,910 And you can notice that if you have five, what he says. 8 00:00:26,920 --> 00:00:28,090 So that's the next item. 9 00:00:28,270 --> 00:00:29,110 But what is this? 10 00:00:29,110 --> 00:00:31,110 Are these corners, right? 11 00:00:31,450 --> 00:00:33,750 That's A, B, C, D and E. 12 00:00:33,970 --> 00:00:36,160 Now, if you have five, what is this? 13 00:00:36,700 --> 00:00:38,920 Then you will have five sites. 14 00:00:41,020 --> 00:00:41,330 Right. 15 00:00:41,500 --> 00:00:44,170 So if you have for dessert, you will have four sites. 16 00:00:44,560 --> 00:00:47,460 All right, now, what are decent sites of a polygon? 17 00:00:47,710 --> 00:00:51,070 These are sites with a common end point. 18 00:00:51,280 --> 00:00:52,470 Let's take an example. 19 00:00:52,630 --> 00:00:56,680 You have site Abe over here and you have over here. 20 00:00:56,890 --> 00:01:04,930 You can see that point B or Vertex B is a common endpoint of these two sites right there for Abe and 21 00:01:04,950 --> 00:01:06,940 B.C. are just in sites. 22 00:01:07,360 --> 00:01:07,760 All right. 23 00:01:07,990 --> 00:01:09,260 Now, what about Atcheson? 24 00:01:09,280 --> 00:01:09,930 What is this? 25 00:01:10,240 --> 00:01:12,820 These are endpoints of the same site. 26 00:01:13,040 --> 00:01:20,260 For example, if you take site Ebbie, you can see that A and B are in points off site. 27 00:01:20,710 --> 00:01:21,070 Right. 28 00:01:21,190 --> 00:01:28,360 Therefore, point and point we are at just in what is now you know, that Anderssen means something 29 00:01:28,360 --> 00:01:33,400 that's next to each other, to adjacent sites are sites that are next to each other. 30 00:01:33,620 --> 00:01:37,930 Similarly are decent vertices, advertisers that are next to each other. 31 00:01:38,140 --> 00:01:38,540 All right. 32 00:01:38,770 --> 00:01:42,780 Now, the last item that we are going to visit over here is diagonals. 33 00:01:43,090 --> 00:01:49,490 Now, if you join two known Addison vertices, you will get a diagonal. 34 00:01:49,810 --> 00:01:53,130 Let's take one of the signals that you can get over here. 35 00:01:53,500 --> 00:01:58,420 If you join E and C, you get A diagonal, you join E and B, you get a diagonal. 36 00:01:58,420 --> 00:02:00,810 Right, because these are all known, Anderson. 37 00:02:00,850 --> 00:02:01,430 What is this? 38 00:02:01,630 --> 00:02:04,790 Now, if you join two, Addison, what is this one example? 39 00:02:04,810 --> 00:02:08,680 And B, that is A side and that's not a diagonal. 40 00:02:08,950 --> 00:02:09,430 All right. 41 00:02:10,660 --> 00:02:16,270 Now, what are the diagonals over here, the diagonals are 80, right, that's 80. 42 00:02:16,600 --> 00:02:22,600 Then you have AC, you have Ebbie, you have E, C, and you have DBI. 43 00:02:22,600 --> 00:02:25,930 So that's five diagonals that you're getting over here. 44 00:02:26,230 --> 00:02:31,450 Now, let's quickly revise the concept that we learned in permutation and combination if it's given 45 00:02:31,450 --> 00:02:33,280 that you have five vertices. 46 00:02:33,650 --> 00:02:36,310 So that's the case over here because it's a Pentagon. 47 00:02:36,550 --> 00:02:41,620 How many diagonals can you form to the number of diagonals of an inside? 48 00:02:41,620 --> 00:02:51,100 And polygon is equal to INSEE to minus in NC two is the number of ways in which you can select two points 49 00:02:51,280 --> 00:02:56,410 from endpoints and you have to subtract N because you will have insights. 50 00:02:56,440 --> 00:02:56,710 Right. 51 00:02:56,950 --> 00:02:58,750 So you have five points over here. 52 00:02:58,900 --> 00:03:03,450 If you select two points from five points, that would be five C two. 53 00:03:04,120 --> 00:03:09,460 But in this case you will also get a decent what is the selected right. 54 00:03:09,470 --> 00:03:10,590 And those are sides. 55 00:03:10,600 --> 00:03:12,370 So you need to subtract that out. 56 00:03:12,670 --> 00:03:19,110 So in this case, you will have five sites, or if you have invertors, you will have insights. 57 00:03:19,450 --> 00:03:25,510 But the number of diagonals over here is five C to minus five, five C two is five in the four by two. 58 00:03:25,840 --> 00:03:26,180 Right. 59 00:03:26,350 --> 00:03:32,680 Which is equal to ten and ten minus five will give you a five, which is what we have got over here.