1 00:00:00,880 --> 00:00:06,370 Let's do this question, the first question says, find the number of diagonals of a triangle. 2 00:00:06,700 --> 00:00:14,680 Now we know that diagonals are obtained when you join non adjacent purposes right now. 3 00:00:14,680 --> 00:00:16,500 What are the words of this triangle? 4 00:00:16,720 --> 00:00:20,890 You have A, you have B, and you have C, you have three vertices. 5 00:00:21,100 --> 00:00:22,730 Now let's take any vertex. 6 00:00:22,750 --> 00:00:30,490 So let's take Vertex B now you can see that Vertex B in this triangle does not have any known adjacent 7 00:00:30,490 --> 00:00:30,880 vertex. 8 00:00:30,880 --> 00:00:38,470 Right is also an adjacent vertex to Vertex B and C is also an adjacent vertex to Vertex B, therefore 9 00:00:38,560 --> 00:00:42,310 you cannot form any diagonal in the case of a triangle. 10 00:00:42,580 --> 00:00:42,920 Right. 11 00:00:43,090 --> 00:00:44,920 And the answer is zero. 12 00:00:45,190 --> 00:00:47,140 So you do not have diagonals in a triangle. 13 00:00:47,380 --> 00:00:48,640 All right, let's move on. 14 00:00:48,820 --> 00:00:51,450 What are the number of diagonals in a hexagon now? 15 00:00:51,460 --> 00:00:54,310 A hexagon is a six sided polygon. 16 00:00:56,160 --> 00:00:58,390 All right, now, let's take an example. 17 00:00:58,680 --> 00:01:00,180 We have a hexagon over here. 18 00:01:00,480 --> 00:01:06,500 Now, remember, the number of diagonals is given by INSEE to minus in right now. 19 00:01:06,500 --> 00:01:08,430 Over here, you have a hexagon. 20 00:01:08,580 --> 00:01:10,990 So in in this case is six, right? 21 00:01:11,070 --> 00:01:12,060 Because it has six. 22 00:01:12,090 --> 00:01:12,720 What is this? 23 00:01:13,170 --> 00:01:15,390 The answer is six to minus six. 24 00:01:15,630 --> 00:01:17,180 That gives us six in two. 25 00:01:17,190 --> 00:01:19,920 Five by two minus six. 26 00:01:19,920 --> 00:01:20,270 Right. 27 00:01:20,520 --> 00:01:21,240 But what is this? 28 00:01:21,240 --> 00:01:25,020 That 15 minus six, which is equal to nine. 29 00:01:25,050 --> 00:01:26,130 So let's see. 30 00:01:26,310 --> 00:01:27,210 Is that correct? 31 00:01:27,640 --> 00:01:29,250 Over here, let's take this vertex. 32 00:01:29,460 --> 00:01:31,870 Let me join it with its non Anderson. 33 00:01:31,890 --> 00:01:32,490 What is this? 34 00:01:32,850 --> 00:01:35,310 So that's three diagonals that I get here. 35 00:01:35,700 --> 00:01:38,520 Remember, if I join these two, I get a side. 36 00:01:38,520 --> 00:01:42,820 I do not get a diagonal because these two vertices are just what is this? 37 00:01:43,080 --> 00:01:44,190 All right, let's move on. 38 00:01:44,340 --> 00:01:49,140 Let's take this vertex over here and join it to its non Anderson. 39 00:01:49,170 --> 00:01:49,800 What is this? 40 00:01:50,520 --> 00:01:53,550 I get again, three diagonals over here. 41 00:01:53,790 --> 00:01:55,520 Now, let's take this one over here. 42 00:01:55,800 --> 00:02:00,240 I get two more over here because this one is already drawn. 43 00:02:00,240 --> 00:02:01,890 So I don't double counted. 44 00:02:02,040 --> 00:02:04,830 So I get two more over here and over here. 45 00:02:04,830 --> 00:02:06,570 I get one more diagonal. 46 00:02:06,570 --> 00:02:07,830 Is there any more diagonal? 47 00:02:08,040 --> 00:02:09,360 No, right over here. 48 00:02:09,360 --> 00:02:11,520 I have already joined it to this point. 49 00:02:11,670 --> 00:02:14,910 I've joined it to this vertex and I've joined it to this vertex. 50 00:02:14,910 --> 00:02:20,250 Similarly for this vertex, also, I have joined two three other known adjacent. 51 00:02:20,250 --> 00:02:25,710 What is therefore the answer is three plus three plus two plus one. 52 00:02:25,710 --> 00:02:26,100 Right. 53 00:02:26,670 --> 00:02:28,250 Which gives you the answers. 54 00:02:28,560 --> 00:02:31,530 Nine to three plus three plus two plus one. 55 00:02:31,950 --> 00:02:36,890 B over here, three over here to over here and one over here. 56 00:02:36,900 --> 00:02:38,280 That is also equal to nine. 57 00:02:38,490 --> 00:02:43,410 And that's the same answer that we got when we did six to minus six.