Class 6 Maths Chapter 5 | Understanding Elementary Shapes Full Chapter Explanation| INSIGHTFUL MATHS
Class 6 Maths Chapter 5 | Understanding Elementary Shapes Full Chapter Explanation| INSIGHTFUL MATHS
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00:00Hello everyone. Welcome back to Insightful Maths. In today's session, we are going to
00:05discuss this topic, Understanding Elementary Shapes. It is chapter number 5 of class 6.
00:12So all the important topics in this chapter we are going to discuss. This is basically
00:17an introduction video. I'll just give you a glance what all will be covered in this
00:21video. We'll talk about angles and revolution, clock and the revolution, the part of the
00:29clock, the angles and all those questions related to clock, like clockwise, anticlockwise,
00:36angles, the different type, for example, acute, obtuse, reflex, all those angles, what is
00:43the meaning of perpendicular and perpendicular bisector, naming the triangles, bases, the
00:49angles and the length of the side and finally the polygons. Okay, we are going to discuss
00:55all these things in the chapter. So what you are requested now to please ensure you
01:00watch the video till end and I'll ensure that you get the insight of all the topics. So
01:07let's begin. The first topic now, we need to understand the directions, the angles between
01:15these directions and if we are going clockwise or anticlockwise, what changes are it going
01:22to make? Okay, so we are first talking about the directions. We all know how many directions
01:29are there. Basic four directions are there, east, west, north and south. Okay, basic four
01:37directions are there. Please mind the location of these directions. It's not like if we have
01:44interchanged them, if we remember this is west and this is east, so undoubtedly your
01:50question will go wrong. So you have to remember, east opposite to east is west, up is north
01:57and down is south. Okay, these are four directions. Just remember it like a plus sign. Okay, when
02:05two lines cross each other like this and the angle between them is equal to 90 degree and
02:1290 degree is what? This is known as a right angle. Looking at this, are we able to understand
02:17that four 90 degrees are formed here. 90 here, between these two, again 90, this is
02:26again 90 and this angle is again 90 degree. Okay, now between the four, between north
02:33and east, 90, east and south is 90, south west again 90 and north and west is again
02:4090 degree. Now, before doing the questions or going further, let us understand what is
02:46the meaning of clockwise and anticlockwise. Let me take you to the clock first.
02:52See, if this is 10 o'clock, after 10 o'clock, where will this hour hand go? It will go to 11, after 11 it will go to 12, after 12 it will go to 1.
03:04So that means clock moves like this. Okay, how will it come from here? It will go down, down, down, down, down and then up.
03:12So, any clockwise direction means we are moving like this. Anticlockwise means we are moving
03:20opposite to the direction of clock. After 10 o'clock, 9 o'clock never comes, we never move back.
03:25So, if we are asked in anticlockwise question, we will go back. If it is saying clockwise, we will go right.
03:33Okay, good to go. I hope this much is understood. So, we can try the questions on the direction sense now.
03:42Now, understand one thing, this complete circle, if I start from north, see, from north to east,
03:51east to south, south to west, west to north again. So, this complete circle is called one revolution.
04:01This is known as one complete revolution. So, can you tell me what is the angle of one complete
04:08revolution? 90, 90, 90 and 90. 90 is repeated 4 times and 90 into 4 is what? It is 360 degrees.
04:24One complete revolution is 360 degree. So, what is half the revolution?
04:39This much distance is covered. So, 90 and 9 is how much? Half of the revolution means
04:45half of 360 and what is half of 360 degrees? That is 180 degree. Right. So, half of the revolution
04:54is what? That is 180. Question may ask you one fourth of a revolution.
05:02Now, we don't have to remember anything. You see, 1, 2, 3 and 4. This total circle,
05:11is it divided into 4 parts? We write the total parts below.
05:17From these 4, if I am saying 1 by 4, I am taking just one part only, this one. So, one fourth of
05:25a revolution, how many degrees are covered in one fourth? It is just 90 degrees and we can
05:31measure from here also. One fourth of a revolution means 1 by 4 of 360. Now, 360 divided by 4 is how
05:40much? That is again 90 degree only. So, you will remember this basic thing. One complete revolution
05:48is 360. Half revolution is 180. One fourth of a revolution is 90 degree. Now, if you have a
05:573 by 4 of a revolution, I have to take this, this and this. 9 x 2 is 18, 9 x 3 is 27. So, 90 is repeated
06:143 times. 3 times 90 is how much? That is 270 degrees. We can calculate it from here also.
06:23Three fourth of a revolution means 3 by 4 of 360. 360 divided by 4 is 90 and 90 multiplied by 3 is
06:33270 degrees. If you have understood this much, you will be easily able to do this question.
06:41Now, my question is, if I am in North, I am in North, I am taking one fourth of a revolution
06:57clockwise. First, you have to understand whether I have to go clockwise or anticlockwise. I said
07:03clockwise. It goes right like this. So, you will cover only this much. Where will you reach? You
07:20will reach East. Another question, if I am in North, I am in South, I am taking
07:33half a revolution anticlockwise. Now, I have to go clockwise or anticlockwise? I said anticlockwise.
07:41It goes right like this. I have to go half the revolution. Start from here and reach here.
07:54Where will you reach? The answer is North. Now, another question, if I say I am at West,
08:05I am at West, I take one and a half revolution clockwise.
08:13First, we have to see whether we have to go clockwise or anticlockwise. I said clockwise.
08:18We will go right. First, one revolution and then half more. Now, if I take one complete revolution,
08:27I will again reach back to West only. So, whether you go clockwise or anticlockwise,
08:34whenever you take a complete revolution, you will be reaching at the same point.
08:38Now, we took one revolution and came to West. I have to go half revolution more clockwise.
08:45Now, how much is the half revolution from West? That is 180 degrees. Where did we reach? East.
08:52That's my answer. This is about if any fraction is given 3, 4, 2, 4. So, if I ask you a question,
09:03I am at South. I am at South. I am going 3 by 4 clockwise. Where will I reach? I am also in South.
09:14I have to go 3 by 4 clockwise. Now, you see, clockwise means I have to go like this.
09:20Clock goes like this, right? 1, 2, 3, 4. How many parts do I have to take from 4? 3 in the
09:28clockwise direction. If I go like this, 1 part taken, 2 part taken, 3 part taken. So, where have
09:37I reached? East. That's your answer. If the question is asked in the terms of right angle,
09:47between each two consecutive directions, there is a 90 degree angle.
10:08So, if I go down from East, it will be clockwise. The question is saying I have to move anticlockwise
10:15towards South. So, I have to go in the opposite direction towards South. The question is saying
10:21how many right angles will be covered? You see, between these two, 1, 1 more and 1 more. So,
10:29how many right angles are covered? 3. That's your answer. I hope this topic is understood.
10:36Let's move to another topic now. Angles and revolution, I told you. Revolution is 360.
10:42What is 1 by 2, 3 by 4? Clock questions, now we'll be doing. Direction, we have just discussed.
10:48Revolution, we have just discussed. Now, I'll talk about something related to clock.
10:55This is exactly same as like we have done directions. First of all, let me split this
11:01clock in four equal parts. Let's say this is divided in four equal parts. Likewise,
11:31right? So, I have covered 360 degrees.
11:36Then it will be very much easier for us to do these questions even without clock.
11:43I have started from 12. Just a minute. Yes, I have started from 12. Then taking clockwise,
11:51I have come back to 12. So, one revolution is 360 degree.
12:02This is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12.
12:23That is equal to 360 degree.
12:26If the value of 12 revolution is 360, what is the value of 1 revolution?
12:31That is 360 divided by 12. Is it equal to 30 degree?
12:36Now, our work has become very easy. If I ask you, the clock of the needle moves from 12
12:42to 1. So, how much angle has it covered? It is just 30 degree.
12:47It has come from 1 to 2. How much angle has it covered again? Again 30 degree.
12:53It has come from 2 to 3. How much angle has it covered again? Again 30 degree.
12:59Now you see, 30, 30, 30. If you add all three, it is giving you 90 degree.
13:05Is this angle 90 degree? Yes, of course, it is 90 degree. It is tallied.
13:11So, between any two consecutive numbers, consecutive means one after the other,
13:16between those two numbers, the clock always has an angle of 30 degrees.
13:21Correct? Okay. So, now, the question will be coming to you like 1 revolution,
13:28half revolution, or one right angle, two right angles. That you need to understand.
13:36One right angle. We just saw this. This is a right angle, right?
13:40So, remember this. One right angle in a clock means 90 degree. It is equal to three jumps.
13:48You will be able to cover all the questions easily.
13:56If I come from 12 to 3, it is 90 degree, one right angle.
14:01So, I know that whenever the question will say that I am at some time,
14:06I have to go one right angle. So, how many jumps will I take? I will be taking three jumps.
14:11So, if one right angle is three jumps, then what should be the two right angles?
14:17Three times twice, that is six. What should be the three right angles?
14:21See, one right angle, three jumps. The second right angle is also three. Six jumps are done.
14:27If I take one more right angle, three right angles, three more will be added, nine jumps.
14:32If I take four right angles, that is 12 jumps. It is easy.
14:37Now, you see, if the question says, I am at 12 o'clock. Okay. I am at 12 o'clock
14:46and I take half a revolution clockwise. Now, you see, there is a common sense in
14:52all the clock questions. The clock never goes anticlockwise.
14:57So, all the questions of the clock, whether you are given clockwise or not, it is but obvious,
15:03you will take it clockwise. Okay. Do not get confused that we do not know whether to go
15:08clockwise or anticlockwise. The clock will always go clockwise. Correct.
15:13So, my question is, I am at 12 o'clock and I have taken half a revolution.
15:21Okay. Where will I reach?
15:27Let me just divide this in four equal parts.
15:31How much do I have to go? Half of a revolution. What is the whole circle? One revolution.
15:36So, half of one. So, where do I have to reach from 12? Six. That's my answer.
15:43If I say, I am at, let's say, three o'clock. I am at three o'clock. I have to cover three-fourth
15:51of the revolution. Three-fourth means four parts. I have to go three parts ahead.
15:58One, two, and three. Where will I reach? 12 o'clock.
16:05Now, let's do the questions wherein it is given in the terms of 90 degree or the right angle.
16:16And I turn through one right angle. Where will I reach?
16:27One, two, and three.
16:34So, 12 plus three. 12 is a 12 o'clock. So, finally, one, two, three.
16:43So, ideally, 15 means it is three o'clock.
16:49Now, my question is, if I am starting from two o'clock.
16:52Okay. I am starting from two o'clock and I turn through one right angle. Where will I reach?
17:06I told you, one right angle means three jump.
17:14So, two plus three. Answer is five o'clock.
17:18If I start from four o'clock.
17:25If I start from four o'clock and I turn through two right angles, what will be the final time?
17:33Two right angle means three in one right angle and three in the other right angle.
17:42I have to move six steps forward.
17:45So, four plus six, you will be at 10 o'clock. Easy. Good to go. One more question.
17:53If I am at 10 o'clock, I have to turn through one right angle. Where will I reach?
18:01That is three steps. So, 10 plus three is 13.
18:08It will be at one o'clock only because we are talking about a 12 o'clock.
18:1510 ke baad one jump, two jump and three jump. So, your final answer will be one o'clock.
18:22I hope it is making the concept easier for you. You are not required to make and jump,
18:29you know, just calculate using this clock. Just remember it with the number of jump.
18:35One right angle, three jump. Two right angle mein double, six. Three right angle mein triple,
18:41nine. Four right angle is 12 jump. Between any two consecutive number,
18:45yeh jo angle hota hai 12 aur 1 ke beech mein 30, 1 aur 2 ke beech mein bhi 30, 2 aur 3 ke beech mein
18:52bhi 30. Right? Let's move to another topic now. Clock wale questions humne abhi dekhe,
18:59the angle meet. Let us talk about the angles first, the basic angles. We know that all the angles
19:07which lie between 0 and 90. Agar mera koi bhi angle hai, wo 0 se 90 degree ke beech mein hai.
19:16That is known as an acute angle. Do rays ke beech mein bahut hi chhota distance hota hai. Right?
19:23Aise saare angles will be called as acute. Now, abhi mene bola it should be less than 90.
19:31Agar yeh 90 ke equal ho jata hai, like this. Between two rays, the angle is 90. It is known
19:39as right angle. Right angle looks like this L. Ab ho sakta hai yeh ray aur door chali jaye,
19:47something like this. So this 90 has increased and the distance between two rays is quite
19:54farther apart. Now the name of this angle which is more than 90. Yeh 90 se bada hona chahiye,
20:02but it should be less than 180. This angle is known as your obtuse angle.
20:09Thek hai, obtuse angle. Ab yeh ray aur door chali gayi, so it will look like this. To abhi
20:16aapka straight line ban jayega na. Angle on a straight line is equal to 180 degree.
20:23And that is known as a straight angle. Thek hai. Now, this is the ray. Abhi yeh straight
20:30angle tak kauch gayi hai. Now this ray is going further apart. Yeh yaha se chalti hui aa rahi
20:36hai and it has gone down. Is this angle more than 180? So more than 180 angles, this bigger angle,
20:44which is even more than 180, these angles are known as reflex angles. So reflex angles are
20:51the angles which are more than 180 and less than 360. Thek hai. Let us talk about this topic now.
21:00What is a perpendicular or a perpendicular bisector? Very important topic. Ab hum do
21:06cheez dhyan se dekhte hai. Is this a line segment? This is also a line segment. Whenever any two
21:16lines or two line segment intersect each other. Intersect ka matlab cross karna. Whenever these
21:23two lines or line segment cross each other at 90 degree angle. Yeh jo angle 90 degree hai na,
21:31these two lines or line segments are known as perpendicular to each other. Perpendicular means
21:38when they are intersecting each other at 90 degree. Thek hai. Iska matlab hai perpendicular.
21:44There is one more word bisector. Ab yeh bisector kya hota hai? Bi means two. Okay. Bi means two.
21:53Sector means two parts. Toh abhi jo mera yeh line segment hai na, yeh is line pe kahin bhi jaa
22:00sakta hai. But it has to cut through 90 degree. But agar yeh line segment exactly middle of this
22:08line segment se jaata hai and it is breaking it in two equal half. Bilkul centre se gaya yeh wala
22:15aadha part aur yeh wala aadha part agar equal hai. Toh is particular line segment ko hum bolenge
22:22perpendicular bisector. Why perpendicular? Kyunki yeh wala angle 90 hai. Why bisector?
22:30Because at this point it has divided the line segment in two equal part.
22:36Thek hai. Dubaara sochiye. Agar mere paas ek line segment hai, let's say 4 centimetre.
22:43Iska middle point kaha par hoga? 2 centimetre here, 2 centimetre here. It is the middle point.
22:50Agar is middle point se koi bhi ek line segment aise pass karta hai. Like this. Which is making
22:58an angle of 90 degree. Yaha par 90 degree bhi bana raha hai. Jis point se paas kar raha hai,
23:04waha par is line ko 2 part me split kar diya. Yeh kya hai? Yeh ab ek perpendicular bisector hai.
23:10Toh agar aap se poocha jaye, kya yeh line perpendicular bisector hai? Your answer is yes.
23:16Because it has broken the given line in two equal half. Thek hai. Ab aap is diagram me dekho,
23:23while doing this question the concept will be clear to you. Is CE equal to EG? Ab yeh CE kya
23:30hai? CE matla distance from here to here. Hum jab number line pe distance dekhte hai na,
23:36it is calculated as units. Ab aap dekho CE se D ke beech mein sirf ek jump hai,
23:43ek jump yaha. Toh can I say the distance CE is just 2 units? Hai na, do baar jump liya,
23:492 units. What is EG? E se F, F se G. Yeh bhi 2 unit hai. Toh kya mein bol sakti hoon yeh wala
23:58distance aur yeh wala distance equal hai? Answer is yes. Humne abhi abhi dekha,
24:03CE and EG, they both are 2 units, the distance is equal. Ab yeh wala jo line hai M, aap se
24:11poocha hai, does PE bisect CG? Yeh point hai P, yeh point hai E. Hum kisi line ko naam kaise
24:21dete hain by taking any 2 points on the line? Aap se poocha hai, yeh wali jo given line hai,
24:27this one, is it a bisector? Bisector ka matla maine aapko abhi abhi bataya tha,
24:34bisector means which passes through the centre. Kis line ke centre se line ka naam aapko given
24:40hai CG. This is C, this is G. Ab ab dekho, 1, 2, 3, 4. Yeh 4 units tha. 2 units here,
24:492 units here. Is it passing through the centre? Bilkul haan yeh toh centre se ja rahe hain. So
24:54that means this line PE is the bisector. This is true. Identify any 2 line segments for which PE
25:04is the perpendicular bisector. Ab aapko 2 line segment ka naam batana hai jiska PE is the
25:11perpendicular bisector. The line PE is perpendicular to sabhi ke hi hai because it is
25:20making an angle of 90 degree. Bisector tab hoga jab left portion right portion dono equal ho.
25:27Toh hum kya karte hain, one position left, one position right. Kya line segment mila mujhe
25:34itna sa? Iska naam kya hai? Yeh point is D, this point is F. Toh ek line segment mujhe mila D,
25:41F. Kyonki left ka aur right ka distance should be equal. Ek humne abhi abhi dekha tha CG,
25:48hum usko nahi lenge. Usme do do step gaye the na. Ab main kya karte hain, ek pehle se left hai,
25:542 and 3. 3 steps left ho gaye na, ab 3 step right chalte hain. 1, 2 and 3. Ab dekho,
26:033 right, 3 left. Is this line passing through the center? It is yes. Let us name this line,
26:10yeh point hai B, yeh point hai H. So that means yeh jo perpendicular bisector hai, yeh DF ka bhi
26:19hai, yeh BH ka bhi hai. This is how we decide whether the given line segment is a perpendicular
26:27bisector or not. Okay, now you have to tell these statements if these are true or false. Yeh ekdum
26:35asaan hai, I am pretty sure you will be able to do this. Let us discuss the answers. AC is greater
26:41than FG. AC kitna hai? 1 and 2. This is 2 units. FG is just 1 unit. Is 2 greater than 1? Of course,
26:51answer is yes. Toh jab aap paper mein answer attempt karte hoon na, aapko dikhana hai ki AC
26:57jo hai, it is equal to 2 units. You have to write like this. AC is equal to 2 units. Then you have
27:04to tell FG is equal to 1 unit. Since 2 is greater than 1, this is true. Next is CD equal to GH. Aap
27:14CD kitna hai? CD is 1. GH is also 1. Are they both equal? Answer is yes. Another one is BC.
27:27BC is this one. Just 1 unit. It is lesser than EH. EH se H. Ek, do, teen. EH is 3. 1 is less than 3?
27:38This is again true. Theek hai? So I hope this concept of perpendicular and perpendicular
27:44bisector is also understood to you. Alright, moving on to the next very interesting and one
27:52of the most important topic now, classification of triangles.
28:09If I have a triangle, dekho triangle aise bhi deekh sakta hai, triangle aise bhi deekh sakta
28:16hai, triangle aise bhi deekh sakta hai. Triangle kya hota hai? Any three-sided polygon, jiski
28:23teen side hoti hai aur wo close ho, usse hum triangle kehte hai. Aap hum sanjhenge iske naam
28:29hum kaise dete hai? How to name the triangles? Agar mere paas ek triangle hai, sabse pehle
28:36hum seekhenge, base is the length of the side. Agar mere paas ek triangle hai, jiski teen
28:44side equal hai. Yeh bhi 3 cm hai, yeh bhi 3 hai, yeh bhi 3 hai. Sabse pehle main baat
28:52kar rahe hoon, naming the triangle's base is the length of the side. Agar teen side
28:58equal hai, isse aap bologe equilateral. This is known as equilateral triangle. Dubhara
29:06dhyan do, maine yaha par angle ki koi baat nahi kari. I am talking about the length of
29:11the side, this is equilateral triangle. Doosra triangle hum dekhte hai, jahaan par teeno
29:17mein ek bhi side equal nahi hai. Maan lo, ek side hai 3, ek side hai 4, ek side hai
29:265. Yaha to teeno hi unequal hai. Jab teeno equal thi, equilateral, teeno equal nahi
29:32hai. This is known as a scalene triangle. This is known as a scalene triangle. One last
29:40kind of triangle is now, where two sides are equal. Maan lo, aise hai, aise hai and
29:48this one. Let's say this and this, yeh bhi 4 hai, yeh bhi 4 hai, yeh bhi 5 hai. Two side
29:55equal hai na. Aise triangle ko hum bolte hai isosceles. Please mind the spelling. All
30:03three equal, equilateral. Koi bhi equal nahi hai scalene. Only two are equal. This is
30:09known as isosceles. Yeh hume samajh mein aagaya. Abhi tak humne sirf side ki baat kariye, humne
30:15abhi angle ki koi baat nahi ki. Now we'll name the triangles as per the angles made
30:24inside it. Sabse pehle sabse aasan triangle lete hain jo hum sab ko pata hota hai. Right
30:31angle kya hota hai? Right angle is the angle wherein one of the angle is 90 degree. Agar
30:39main yeh aisa ek triangle lete hain, jiska koi bhi ek angle, do nahi ho sakte, jiska
30:45koi bhi ek angle 90 degree hai, yeh 90 degree hai na, isse hum bolenge right angle triangle.
30:53Right angled triangle. Koi bhi aisa triangle jisme ek angle 90 degree hai, usse hum bolenge
31:01right angle triangle. Another one is jahaan par teeno angle acute hai. Measure unka kuch
31:08bhi ho sakta hai, humein koi farak nahi parta, kitna bhi measure ho, lekin agar teeno angle
31:1490 degree se chote hain. Maan lo yeh 60 hai, yeh 70 hai, yeh 50 hai. Aap dekho teeno ke
31:22teeno angles are less than 90. Less than 90 ko kya bolte hain? Acute. So iss triangle
31:28ko hum bolenge acute angled triangle. The last one is now, jahaan par ek angle is triangle
31:40mein bahut hi zyada bada hai. Can we identify this angle? Aap dekho, do rays ke beech mein
31:46kitna zyada distance hai, lekin straight line nahi baniye abhi bhi, but it is more than
31:5290 degree. Aise angle ko hum kya kehate hain? Obtuse angle. So this triangle is your obtuse
31:59angled triangle. Itna aapko pata hona chahiye. Equilateral, scalen and isosceles. Base is the
32:07length of the side. Angle ke hizaab se agar ek angle 90 right angle, saare angle less than 90
32:14is acute angle. Ek angle more than 90 and of course less than 180, that is obtuse angled
32:22triangle. Aap kisi kisi case mein aapko yeh dono mix karke de dete hain. So you need to know how
32:30to name it. For example yeh right angled triangle hai. Thik hai? Humme dikh rahe hai na right
32:35angle hai. Do 90 degree, yahan pe 90 degree ka angle hai. Agar main aapko bolte hu yeh side 4
32:41hai. Third ka mujhe nahi pata. How to name this triangle? Aap mujhe angle bhi pata hai,
32:47mujhe do side bhi pata hai. Third ka mujhe koi matlab nahi hai. Jo given information hai,
32:52I will be naming it as per it only. Aap ise bologe, ab aap dekho jahaan par do side equal
32:59hoti hain, usse kya bolte hain? Isosceles. To aap in dono naam ko club kar doge. Aap pehle
33:05likhoge as per the side. It is isosceles and what kind of triangle? Right angled triangle.
33:13Thik hai? Yeh wala dekho. Ab yeh 60, 70, 50. Agar main aapko bolte hu yeh 3 hai, yeh 4 hai,
33:22yeh 5 hai. Aap mujhe teeno side bhi pata hai, teeno angle bhi pata hai. Agar teeno side equal
33:28nahi hai, usse kya bolte hain? Scalon. Aur yeh saare angle acute hain, to acute bhi hua,
33:34your answer will be scalon acute angle triangle. Thik hai? It's very easy. Is angle mein dekho,
33:43obtuse angle mein. Agar main aapko bolte hu, yeh wala side hai 3, yeh bhi hai 3, and let's say
33:50this is 4. Aap ise kya naam doge? Obtuse to yeh hai hi hai. Agar do side equal hoti hain,
33:56to hum usse kya bolte hain? That is isosceles. To aap iske pehle isosceles laga do. Isosceles
34:02obtuse angled triangle. Thik hai? Let us do the practice of these given questions.
34:10Then you will be able to do the questions easily on this topic. Aap pehla aap question dekho,
34:16there is a triangle wherein all the 3 sides are not equal. Ek 7 hai, ek 8 hai, ek 9 hai.
34:24Agar 3 ho equal nahi hoti, usse hum kya bolte hain? That is known as a scalon triangle.
34:31First one is easy. Hume angle ke baare mein kuch nahi pata tha, to main acute,
34:37obtuse, right yaha kuch nahi lagaya. Thik hai? Second part. Aap dekho mujhe firse sirf sides
34:43given hai, angle nahi given. To hum isme right angle, obtuse angle, acute angle kuch nahi lagayenge.
34:50Agar 3 ho side, 1, 2, 3, dubaara 3 ho ekdum alag hai, it is again known as a scalon triangle.
35:00Next one. Mere paas ek triangle PQR hai. Ek side, do side, teen side. Teen ho side 5 cm ke equal
35:09hai. Agar teen ho side equal hoti hain, to hum usse kya bolte hain? That is known as an equilateral
35:16triangle. D part. Aap yaha par angle ki baari aadi. Mujhe yaha length of the side given hai
35:23kahin? Length of the side to kahin nahi given. Lekin itna pata hai ki teen ho angle mein one of
35:28the angle is 90. To jahaan par ek angle 90 aata hai, uss triangle ko kya kehate hain?
35:34It is simple. It is just right angle triangle. Hum isme scalon, equilateral, isosceles kuch nahi
35:41likhenge. Hume pata hi nahi length of the sides kya hai. It could be anything.
35:45Next one. A triangle XYZ, jahaan par M angle Y means measurement of angle Y. Ye
35:52mein aapko bana ke dikhati hoon so that you can visualize. What does it mean?
35:58It is saying, ek triangle mere paas XYZ hai, jahaan par angle Y 90 hai. Is angle Y ko humne
36:05banaya 90 degree. Further, ab ye Y hai to ek X hona chahiye, ek Z hona chahiye hai na,
36:11tabhi to triangle banega. XY aur YZ equal hai. Iska jitna bhi length ho. Hume koi farak
36:17nahi padta. Hume bataya hai XY aur YZ. Jitna bhi aap length loge, aapko ye dono equal lena hai.
36:24Ab mere paas tha ye triangle hai. I have to name it. Ab mujhe do cheezein pata hai yaha pe.
36:30Dekho ek angle 90 hai. To mere answer mein right angle triangle to aayega hi aayega.
36:36Lekin do side bhi equal hai. If two sides are equal, this is known as isosless and then continue
36:45right angled triangle. Because two sides are given equal, it is isosless right angled triangle.
36:56Third one, the last one now. A triangle is given jahaan par ye teen angle ka measure hai. Teeno
37:03angles are less than 90. Am I being given any side here? Mujhe length of the side to nahi pata.
37:10Sir teeno angle pata hai which are less than 90 degree. So the name of this triangle will be acute
37:17acute angled triangle. Another category of questions is wherein a picture is being given
37:30to you. Aapko kuch likhne mein nahi given hai. Aisa pictures given hai. Ab aapko iska naam dena
37:36hai. Ab aap dekho one two three. The length of three sides are given to you aur do side equal
37:45hai. Agar do side equal hai toh kya bolte hain hum usse. This is known as isosless triangle.
37:54Agar aap dekho yahaan par measure bhi de rakha hai. Measure ka value nahi hai,
37:58but dekhe hume pata chal raha hai ye saare less than 90 hai. So you can name it like isosless
38:04acute angled triangle. Hum isko aise naam de sakte hain. Next one now. One two three. Teen
38:13side hai. Teen ho hi alag hai. And this angle. Can we make out this angle is 90 degree. Ye toh
38:21right angle bhi hai. Do cheez ho gayi. Teen ho side equal nahi hai. Toh pehle aap likhenge
38:26scale in. And since one of the angle is right angle. Right angled triangle. Okay. Third point.
38:35Ye dekho kitna bada angle hai. Is it right obtuse acute. Aise angle jo 90 se zyada hote
38:44hai. Jo itna bada distance hai. Toh obtuse hota hai. And two sides are equal. Agar two sides equal
38:51hai. That is known as isosless. Toh aap isse bologe isosless obtused angled triangle.
39:02Isosless obtuse angled triangle. In the similar manner. Dekho ye obtuse. Teen ho not equal.
39:10Scale in obtuse angled triangle. Yaha par angles ke baare mein koi baat nahi hui. Teen ho side
39:17equal. This is equilateral. Again I have a 90 degree angle and two sides equal. Do side equal
39:25hongi. Toh kya bologe. That is isosless. And one side. This is equal to 90 degree. So this is a
39:34right angled triangle. Right. I hope this topic is becoming easy for you.
39:41All right. Now a quick recap of the kinds of quadrilaterals. Quadrilateral basically kya
39:48hota hai. Pehle aap samjho what is a polygon. Polygon is a closed figure which is made up of
39:56only line segments. Agar main aise circle banati ho na. Circle bhi close hai. Lekin ye line
40:02segment se nahi bana. This is not a polygon. Agar main aisa kuch banati hoon. Ye line segment se
40:09bana hai. Lekin ye close nahi hai. This is also not a polygon. Sabse chota polygon which we can
40:16make is a triangle. Kam se kam teen side chahiye hoti hai ek close figure banane ke liye.
40:22Theka hai. Toh aisa polygon jisme four sides hoti hai usse hum bolte hai quadrilateral.
40:29Aap aap dekho in toh saari figure mein hi four sides hai. Chaaron line segments se
40:33hi milke baniye. In sabhi ko hum bolte hai quadrilateral. Quadrilaterals ke alag alag
40:39naam hote hain. Basis different properties of these figures. Rectangle hum sabko malum hai.
40:47Opposite sides are equal. This and this equal. This and this equal. Rectangle mein kya hota hai.
40:54Opposite sides are equal. Saari ki saari corner angles are 90 degree. Theka hai. Ye hume already
41:01pata hai. Similarly for a square, all the four sides are equal. One, two, three, four. Saari
41:09side equal. Saari interior angle 90. Ye bhi hume pata hai. Now what is a rhombus? Parallelogram
41:16I will just tell you. Pehle rhombus pe aajao. Rhombus also has all the four sides equal.
41:23Jaise square mein tha na. Similarly in rhombus also all the four sides are equal. What is the
41:29difference? Aap dekho yaha par saari interior angle 90 the. Rhombus mein aisa nahi hota.
41:35All the four angles are not 90. They are not equal. Only the opposite angles are equal.
41:41Angle B aur angle D. Ye barawan hunge. Inka kitna bhi value ho. Similarly,
41:47angle A and angle C will also be equal. Theka hai. This is a rhombus. All the four sides are equal
41:55and opposite angles are equal. Now comes a parallelogram. Parallelogram is a quadrilateral
42:03jahaan par opposite sides are equal and parallel. Opposite side. Ye wala side is wali side ke equal
42:11bhi hai aur parallel bhi hai. Similarly, ye wala side is side ke equal bhi hai aur parallel bhi
42:17hai. Theka hai. Toh agar aapse koi pooche ki rectangle. Kya rectangle ek parallelogram hota
42:23hai? Toh you need to identify, you need to prove whatever the properties of parallelogram are
42:29there. Parallelogram kis figure ko hum bolte hain? Jahan pe opposite sides are equal and parallel.
42:34Toh humein ye check karna hoga. In case of a rectangle. Kya opposite sides equal hai?
42:41Yes opposite sides toh equal hai. Are they parallel? Dekho ye dono ek doosre ke parallel
42:47hai. Ye dono ek doosre ke parallel hai. Toh rectangle mein toh parallelogram wali sari
42:53properties hain? Answer is yes. Rectangle is also a special parallelogram. Similarly,
42:59kya square bhi ek parallelogram hai? Opposite sides equal and parallel.
43:05Opposite sides equal and parallel. Ye bhi ek parallelogram hai.
43:10Rhombus. Opposite sides equal parallel. Opposite sides equal parallel. Ye bhi ek parallelogram hai.
43:18Come to now the trapezoid or the trapezium. Trapezium is a quadrilateral which has just
43:25one pair of parallel sides. Parallelogram mein do pair the. Trapezoid aur trapezium mein
43:31koi bhi ek pair of parallel side hona chahiye. Aap dekho ye side aur ye side they are parallel
43:38to each other. Parallel means the distance between them will remain the same. They will
43:42not be cutting, intersecting or meeting each other ever. Agar main in dono line ki baat karo,
43:48aap dekho hum in dono ko parallel kyu nahi bol rahe hain? Agar main isko extend kar deti hoon.
43:53Like this. And I extend like this. At some point of time they will cross each other. Dekho cross
44:01ho rahi hai na. Toh parallel lines toh kabhi meet nahi hoti. Toh ye dono toh parallel hoi
44:06bhi sakte hain. Ye toh kuch time baat cross karengi. So parallel lines ka unka length se
44:12koi lehna dena nahi hain. Parallel means ye kitna bhi main isko extend kar doon they will never be
44:19crossing each other. They are parallel lines. And this is a trapezium because it has just
44:26one pair of parallel side. Last one is a kite. This kind of figure. It has two pairs of adjacent
44:34side equal. Adjacent matlab hota ek boosre se juda hua. One pair equal, another pair equal
44:42and opposite angles are also equal. Theek hai. This is a kite. So I hope till here you are able
44:49to understand the things. Right? After this what you are supposed to do, please try to do the
44:55NCRT questions and if any doubt is there in any of the topic, you may please comment on this video.
45:02Ok. So I hope you enjoyed, you got the clarity. If you have not liked and subscribed yet,
45:08please do it right now. Thank you so much for watching. Take care.