A relaxing geometry problem.

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Michael Penn

Michael Penn

3 жыл бұрын

We look at a solution to a nice and quick geometry problem. Inspired by this:
math.stackexchange.com/questi...
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Пікірлер: 982
@demenion3521
@demenion3521 3 жыл бұрын
if you generalize the problem to n consecutive squares, the first and last of which touching the sides of the triangle, you get a side length of a=(6n-4*sqrt(3))/((n+1)*(3n²-4))
@n8style
@n8style 3 жыл бұрын
nice, this deserves more attention that it's got
@HahaHongKong
@HahaHongKong 3 жыл бұрын
Good
@TacioMedeiros0
@TacioMedeiros0 3 жыл бұрын
Another interesting follow up question would be to calculate the proportion of the right side of the triangle where the last square touches the triangle in terms of n.
@hydraslair4723
@hydraslair4723 3 жыл бұрын
@@TacioMedeiros0 since the last square has side n times a, it's just sqrt{3} times n times a by trigonometry (and expand a in terms of n from the comment above). This is the distance between the point where base and right side touch, and the point where the last rectangle touches the right side.
@ciberiada01
@ciberiada01 3 жыл бұрын
Yeah, but if n→∞, then will the squares form a parabola of the type y = a + b·√x̅ ❓ Or will they form another function? IMHO, it will be a ln(x) + 1
@johnalley8397
@johnalley8397 3 жыл бұрын
I'm liking these take-a-breather problems lately. The deep analysis stuff makes my eyes vibrate.
@nope8729
@nope8729 3 жыл бұрын
Agreed. Topology is giving me a run for my money.
@johnalley8397
@johnalley8397 3 жыл бұрын
@@nope8729 Don't get me wrong, I love the other stuff and am eager to get back to it. I'm just saying this intermission is quite nice.
@kerim0o0
@kerim0o0 3 жыл бұрын
Yes! Haha and it makes your skills in fun problems like this one much much sharper, which is neat! :)
@ellenmarch3095
@ellenmarch3095 2 жыл бұрын
Yeah, I did this one in my head. I feel better about myself now. :-D
@dd6240
@dd6240 Жыл бұрын
Eyes vibrating that could be a medical condition buddy
@guidohaverkort5782
@guidohaverkort5782 3 жыл бұрын
5:18 that 8 is gonna give me nightmares
@Ocean_38
@Ocean_38 3 жыл бұрын
oO
@recklessroges
@recklessroges 3 жыл бұрын
I had a math teacher that used to write 8 starting in the middle, in one gesture. Looked a little like &.
@kilian8250
@kilian8250 3 жыл бұрын
Reckless Roges Isn’t that how everyone does it?
@landochabod7
@landochabod7 3 жыл бұрын
It looked like someone decapitated a snowman...
@gj4312
@gj4312 3 жыл бұрын
@@recklessroges you mean properly?
@pflh2391
@pflh2391 3 жыл бұрын
Me before: math.. relaxing? Haha good joke m8 Me after: dang this is actually relaxing
@Hungabrigoo
@Hungabrigoo 3 жыл бұрын
I literally only watched this because this was the only video I could find that did not contain political bias. Not disappointed though.
@corbenbowen8746
@corbenbowen8746 3 жыл бұрын
@@Hungabrigoo bro seriously. It’s all KZfaq is
@Kyllleur
@Kyllleur 3 жыл бұрын
That's why I could not stay awake during math class.
@danteteeter6567
@danteteeter6567 3 жыл бұрын
Yeah all right but "eh-quilateral" smh
@DistinctGamer_
@DistinctGamer_ 3 жыл бұрын
I felt really proud of myself solving this just by looking at the thumbnail and then watching the video getting slightly excited each time I got a step right
@runik11
@runik11 3 жыл бұрын
Same here, but I am not going to watch the video.
@thebiggestcauldron
@thebiggestcauldron 4 ай бұрын
@@runik11 Same here but I watched only some parts to compare solutions - mine was different but still right.
@goodplacetostop2973
@goodplacetostop2973 3 жыл бұрын
6:08
@minh9545
@minh9545 3 жыл бұрын
@Bhavesh sinha human
@aakashchakrabarty7714
@aakashchakrabarty7714 3 жыл бұрын
What about Ur qna
@xisailuo
@xisailuo 3 жыл бұрын
4:41 would have been pretty okay too
@goodplacetostart9099
@goodplacetostart9099 3 жыл бұрын
Good place to start at 0:00
@mycommentbelike
@mycommentbelike 3 жыл бұрын
Ummm thanks?
@eufalesio1146
@eufalesio1146 3 жыл бұрын
engineer's approach: draw a straight line perpendicular to the base of the triangle, and then with a compass, measure how many a's fit into that line, set an approximation and boom! result.
@eufalesio1146
@eufalesio1146 3 жыл бұрын
got approximately a=0.125
@BadukTov
@BadukTov 3 жыл бұрын
@@eufalesio1146 not bad at all considering a=0.120...
@yahikotendo5631
@yahikotendo5631 3 жыл бұрын
Unless something requires very precise measurement, an engineer doesn't rly waste the time with it.
@JSSTyger
@JSSTyger 3 жыл бұрын
I asked somebody where the Engineer's office one time. They directed me to the rail yard.
@hareshmehta1772
@hareshmehta1772 3 жыл бұрын
@@yahikotendo5631 mathematical analysis would be quicker.
@ulongapo6891
@ulongapo6891 3 жыл бұрын
I showed this problem to my kid and asked her, what is "a"? And she answered, "a" is the first letter of the Alphabet.
@wlijas
@wlijas 3 жыл бұрын
wow it is so crazy that happened very cool man
@ZiRR0
@ZiRR0 3 жыл бұрын
The Head of that Certain Filipino Volcano but it's Called a Mountain, thanks for sharing, but idc if you're kid said that tho, well that's just my opinion so ye
@Seeter1000
@Seeter1000 3 жыл бұрын
my 5 year old child could find a in 2 secs
@steveurkelfromgoosebumps1965
@steveurkelfromgoosebumps1965 3 жыл бұрын
Math master
@janek1031
@janek1031 3 жыл бұрын
Rebecca...
@bbnazir
@bbnazir 3 жыл бұрын
2 things. 1)It's nice when you change things up and do problems like this. So keep doing it. 2)I don't know if you already do. But, a "this is a good place to stop" merch-line wouldn't be a shabby idea. So maybe look into it (If you already haven't)
@darreljones8645
@darreljones8645 3 жыл бұрын
The decimal expansion of the answer starts off nicely, according to my calculator: 0.120345617...
@rileygrill2369
@rileygrill2369 3 жыл бұрын
Could have just called it 3/25 and went home. If a problem like this was on a multiple choice test I would have reverse engineered the answer and saved 5 minutes.
@yashuchiha99
@yashuchiha99 3 жыл бұрын
Correct
@Oo98oO
@Oo98oO 3 жыл бұрын
True ! So I checked if the coherence was kept going further, well it's disappointing : 0.1203456170622227263683718981953968536111823802691138857367040443716550862213565201269066875322935401880162547210692737813056545611
@AbhishekSingh-hy4dm
@AbhishekSingh-hy4dm 3 жыл бұрын
@@rileygrill2369 that's the difference between solving a problem at home and solving in an exam..you shouldnt reverse engineer the answer when you're trying to get better at the subject otherwise youre not learning anything
@rileygrill2369
@rileygrill2369 3 жыл бұрын
@@AbhishekSingh-hy4dm I think being able to solve a problem in the easiest quickest way possible no matter what you’re doing is the real answer. I was able to look at this thing and tell the answer is less than 1/6. Then looking at the rest of the space and knowing one side ratio, sqrt(3) I could estimate the rest. You have a total of 4a vertical distance you need to convert to horizontal distance, so 4(1/sqrt(3)) which I estimated as 4*.6= 2.4. You add that to your 6a distance and get 1/8.4= .119 Without round off error you get .1201. I was able to get 1/8.4 in under 30 seconds without writing anything down or using a calculator. That’s way more useful than doing things the “correct” way.
@ekeebobs7520
@ekeebobs7520 3 жыл бұрын
Since the base side has length 1, we just have to represent the base as a function of a and equate the result to 1. (a/tan60) + a + 2a + 3a + (3a/tan60) = 1. Finish up.
@theslayerez1944
@theslayerez1944 3 жыл бұрын
did the same thing buddy XD
@denverstrong473
@denverstrong473 3 жыл бұрын
Great minds think alike. I did the same thing lol
@TheK2rla
@TheK2rla 3 жыл бұрын
@Abacus It wasn't even basically. It's literally what the guy in the video did.
@carlosenriquevalderramajua3463
@carlosenriquevalderramajua3463 3 жыл бұрын
Why You didnt justo agrup dud
@00sey35
@00sey35 3 жыл бұрын
your channel is really amazing... I just discovered my fascination with maths and your videos are giving me really comprehensible and easily explained maths problems... keep 'em coming bro !
@tarnumm
@tarnumm 3 жыл бұрын
I would have used just similar triangels. The ratio of the hight to half of the equilateral triagles lenght (to get a rectangular triangle) is sqrt(3)/2:1/2=sqrt(3). TIs have to be equal to the left, small triagle, hence sqrt(3)= a/x => x=a/sqrt(3). The same works with the right triangle, therefore sqrt(3)= 3a:(1-x-6a)= 3a:(1-a/sqrt(3)-6a). Solving for a lead to a=sqrt(3)/(4+6sqrt(3)), which is the same as your solution.
@iviewthetube
@iviewthetube 3 жыл бұрын
That's what I did also.
@jurjenbos228
@jurjenbos228 3 жыл бұрын
Agreed. Using tan is a waste of time.
@Hxrb
@Hxrb 3 жыл бұрын
I'm not good at calculating and numbers. But in terms of visual image, I also use same thing as yours.
@wayneblackburn9645
@wayneblackburn9645 3 жыл бұрын
@@jurjenbos228 I did the same. I think using tan just makes this look more complicated than necessary.
@mbarbierif
@mbarbierif 3 жыл бұрын
I did the exact same thing :D
@wudder9819
@wudder9819 3 жыл бұрын
An alternative method would be to do this graphically. [1] Thinking of the bottom left corner of the triangle as (0, 0), we use y=mx+c to graph the left hand edge of the triangle in order to find the distance between the bottom left corner and the first box within the triangle. Substituting the coordinates of the top corner of the triangle (1/2, sqrt3) into y=mc+c, we get the equation y=x(sqrt(3)). As we know that the coordinates (d, a) [with "d" being the distance between the bottom left corner and the box with lengths a] touch y=x(sqrt(3)), we can substitute (d, a) into the equation to find that d(sqrt3)=a. [2] Now that we know what d is equal to, we can now find out what a is equal to by mapping the right edge of the triangle as an equation. As we know that the triangle is an equilateral, we know that the equation of the right hand edge will be a mirror of the left hand edge. Therefore m=-x(sqrt(3))+c, where "m" is just the y of the equation for the right hand edge. Using this function, we can substitute the coordinates of the top corner of the triangle (1/2, sqrt3) to find C and thus the equation m=-x(sqrt3)+sqrt3 (with C being sqrt3). [3] Using this new equation, we can then substitute where the right hand edge touches the third box. We know that the x coordinate of the third box will be 3a+2a+a+d. We calculated that d is a/sqrt3, so we can then substitute that and then get an x coordinate of 6a(sqrt3)+a/sqrt3. We know that the y coordinate will be 3a, as that is the height of the box where it touches the edge of the triangle. Using the coordinates we just figured out, (6a(sqrt3)+a, 3a), and the equation of the right hand side, m=-x(sqrt3)+sqrt3, we can then calculate the value of a. [4] Substituting the coordinates gives us: 3a=-(6a(sqrt3)+a/sqrt3)(sqrt3)+sqrt3, which will then simplify to a=(sqrt3)/(4+6(sqrt3)). Once you rationalise the surds, you will find that a will be equal to 0.1203, which can also be written as (9-2(sqrt(3))/46. If you made it this far, thank you for reading and I hope that I was able to write this in an intelligible way :D
@merc95
@merc95 3 жыл бұрын
Nice to be watching nice Math work on a Saturday evening....what else better to do....😁 thanks!!!!!
@a_llama
@a_llama 3 жыл бұрын
this was actually a nice problem to solve! thanks
@juanixzx
@juanixzx 3 жыл бұрын
Finally, a problem I can do by my own. :333
@nikolaikuzeikin8634
@nikolaikuzeikin8634 3 жыл бұрын
The first good place to stop where I got on my own.
@csabcp
@csabcp 3 жыл бұрын
me too qwq
@kinshuksinghania4289
@kinshuksinghania4289 3 жыл бұрын
Extremely easy going by the standards this channel has set!!!
@akshitkumar9402
@akshitkumar9402 3 жыл бұрын
thats why its relaxing....
@coldandafraid
@coldandafraid 3 жыл бұрын
I love the geometry problems, you talk through them especially well
@dsharma6328
@dsharma6328 3 жыл бұрын
Easiest problem so far. Yes it was relaxing too.
@jonahb6580
@jonahb6580 3 жыл бұрын
It would be relaxing if my brain wasn’t screaming at “eh-quilateral” 😂
@CreamySpoon
@CreamySpoon 3 жыл бұрын
"ee-quilateral", ftw.
@key-tg1ih
@key-tg1ih 3 жыл бұрын
I was relaxing until I read this. Thanks a lot.
@DragoNate
@DragoNate 3 жыл бұрын
A collateral triangle has ekkwill sides.
@thecompanioncube4211
@thecompanioncube4211 3 жыл бұрын
Same here.
@gj4312
@gj4312 3 жыл бұрын
Equidistant is eequidistant?
@alxjones
@alxjones 3 жыл бұрын
The bits on the end are similar to half an equilateral triangle, so the base is 1/sqrt(3) times the height. That means the base of the big triangle is (6+4/sqrt(3))a = 1 so a = 1/(6+4/sqrt(3)).
@xXDarQXx
@xXDarQXx 3 жыл бұрын
My solution as well.
@hydraslair4723
@hydraslair4723 3 жыл бұрын
My solution too!
@Asterisme
@Asterisme 3 жыл бұрын
@@hydraslair4723 Meetoo
@Tiqerboy
@Tiqerboy 3 жыл бұрын
That's how I worked it out as well.
@majan6267
@majan6267 3 жыл бұрын
I paused this at the beginning and solved it myself took some different (but similar) routes (intercept theorem and law of sines) but at the end came to the exact same result, very relaxing indeed, thanks
@wkgates
@wkgates 3 жыл бұрын
As an engineer, I'm pulling my hair out everytime he simplifies after 3:44 😂 how many times can you rewrite the same thing?? A mathematician will show you!!
@mickypoo4622
@mickypoo4622 3 жыл бұрын
I am also an engineer and I agree with you totally! At 4:34 he has a solution for the value of "a" which can be calculated. But then he starts some completely unnecessary "waffle" to "rationalise" it, which is just a waste of time. Once you have the answer there is simply no need to continue messing around with it.
@user-jn4tz1fu8x
@user-jn4tz1fu8x 3 жыл бұрын
@@mickypoo4622 he did say the rest is not necessary tho
@Ethan-ui2rn
@Ethan-ui2rn 3 жыл бұрын
Rationalizing the denominator can give you better decimal approximates and may allow for further simplification of terms that could result in a whole number, something a calculator may miss or not be able to find (although calculators probably do all of that already)
@Ivan-ob3vk
@Ivan-ob3vk 3 жыл бұрын
@@Ethan-ui2rn I agree It is necessery if u want to transform it into some kind of computer program. U rationalize it so u can later have better aproximation. If you have a better aprox. your programm will work faster and will be more relevant to the solution
@camrouxbg
@camrouxbg 3 жыл бұрын
@@Ethan-ui2rn rationalizing the denominator makes it nicer for us to look at and is really a remnant from using slide rules and tables. With calculators and computers there really is no need to do it, other than to make it nicer to read.
@dontsubscribe5912
@dontsubscribe5912 3 жыл бұрын
I am mostly impressed by how te erased the 6 at 4:04
@WiseSquash
@WiseSquash 3 жыл бұрын
every time you post a geometry problem like this one I go to Autocad to replicate it. I find quite fascinating to see how everything matches
@raystinger6261
@raystinger6261 3 жыл бұрын
I use GeoGebra, but yeah, I know what you mean.
@khaledchatah3425
@khaledchatah3425 3 жыл бұрын
same
@x_gosie
@x_gosie 3 жыл бұрын
@@raystinger6261 What he mean? I don't understand
@IoT_
@IoT_ 3 жыл бұрын
@@x_gosie it's some engineering staff that mathematicians are too sophisticated to understand
@mr.nobody1738
@mr.nobody1738 3 жыл бұрын
😂that's same thing i would like to do
@matthewfuerst6456
@matthewfuerst6456 3 жыл бұрын
The jump cut after “18^2?” night be the funniest thing I’ve seen today
@mikan9597
@mikan9597 3 жыл бұрын
後半の計算めっちゃ丁寧で優しいな
@GIRGHGH
@GIRGHGH 3 жыл бұрын
I'm confused, what principle allows you to change the order of subtraction?
@vicniels
@vicniels 3 жыл бұрын
I was going to ask the same. I'm still confused
@MolecularMachine
@MolecularMachine 3 жыл бұрын
Yeah, he changed a negative 54 to a positive 54. That doesn't make sense.
@rayanrahmani9838
@rayanrahmani9838 3 жыл бұрын
@@vicniels He multiplied everything by -1/-1. The negatives in both the numerator and denominator flipped
@paulbla5575
@paulbla5575 3 жыл бұрын
You can view Subtraktion as addition where the second number is negative. Then it works with the commutative law. To change signs you then just take -1 out.
@amnotgenjimain6027
@amnotgenjimain6027 3 жыл бұрын
Alright let me just really quickly summarize this problem: Use trig to calculate the length between the edges of the squares to the corners of the triangles, divide that by the amount of a, you get a.
@zafarb4219
@zafarb4219 3 жыл бұрын
yup, it's an easy problem if you use the 60 degree angles
@potawatomi100
@potawatomi100 3 жыл бұрын
Excellent video. Well done.
@blancaroca8786
@blancaroca8786 3 жыл бұрын
Rescale A=1 and find side L=1+2+3+(1+3)/root3. Dividing all lengths by L we get back required a=1/L
@mangai3599
@mangai3599 3 жыл бұрын
Professor grow your problem solving series. Please make a video on the extremal principle.
@fahadb3142
@fahadb3142 3 жыл бұрын
5:17 Did he just right an 8 by drawing two circles on top of each other. THEY AREN’T EVEN TOUCHING.
@GenNTiva
@GenNTiva 3 жыл бұрын
Yeah I saw it too.
@prometheus5218
@prometheus5218 3 жыл бұрын
This will give me nightmares
@eman99a
@eman99a 3 жыл бұрын
I'm more worried that you don't know Right From Write from Rong.
@GenNTiva
@GenNTiva 3 жыл бұрын
@@eman99a omg thanks for saying it now I’m grinning.
@thecompanioncube4211
@thecompanioncube4211 3 жыл бұрын
He just made an Olaf
@MathswithMuneer
@MathswithMuneer 3 жыл бұрын
Respect from one mathematics teacher to another teacher ❤️
@eliezerchi2371
@eliezerchi2371 3 жыл бұрын
Nice bro! Simply elegant.
@azkal1166
@azkal1166 3 жыл бұрын
Thumbnail: "What is a?" me: "a wHAT?!"
@justinepineda5277
@justinepineda5277 3 жыл бұрын
Viewers: See's math equation Me: SHHHAAAAAAARRKK
@Redmentoos
@Redmentoos 3 жыл бұрын
gura
@wladfiggs
@wladfiggs 3 жыл бұрын
I know most people here watched this video to make them better math students or something like that. But, as an engineer, I see this as an exercise to solve real-world problems, and intuitively look for similar shapes and relations to use in design, maintenance, programming and so on; thus, an answer such as (9-2*SQRT(3))/46 is not very practical, and I would never have stoped there. Now, .120 or 3/25 is close enough. Heck, in woodworking, in a 1" equilateral triangle, x could be 1/8" give it or take. I Still gave it a thumbs up.
@amauta5
@amauta5 3 жыл бұрын
Thanks, man! Entertaining video
@Flum666
@Flum666 3 жыл бұрын
a is a small green box, you can clearly see it on the picture
@TilDrill
@TilDrill 3 жыл бұрын
Yeah as an intellectual the answer may be easy but to most people its not that obvious so they need to have those little equasions.
@rajdeepsindhu9268
@rajdeepsindhu9268 3 жыл бұрын
I don't get it...
@blancaroca8786
@blancaroca8786 3 жыл бұрын
@@rajdeepsindhu9268 ...it is akin to the joke where Johnny shouts out “Sir I found x! Look there it is”, pointing with his finger
@rajdeepsindhu9268
@rajdeepsindhu9268 3 жыл бұрын
@@blancaroca8786 Ah, got it :D
@blancaroca8786
@blancaroca8786 3 жыл бұрын
@@rajdeepsindhu9268 Well I might be wrong as the “a” would be a small white box while the triangle is green?
@MarcoLiedekerken
@MarcoLiedekerken 3 жыл бұрын
Better use X in terms of A (instead of A in terms of X). 4X + 6 ( sqr(3) X ) = 1 ( 4 + 6 sqr(3) ) X = 1 X = 1 / ( 4 + 6 sqr(3) ) A = sqr(3) X = sqr(3) / ( 4 + 6 sqr(3) ) A = 3 / ( 4 sqr(3) + 18 ) A = ( 9 - 2 sqr(3) ) / 46
@AngelVazquez-xh1dh
@AngelVazquez-xh1dh 3 жыл бұрын
Why is it better?
@mss11235
@mss11235 3 жыл бұрын
@@AngelVazquez-xh1dh It is practice to keep roots in numerators. This method basically inverses the approach in order to avoid having to complete the square or something weird to get the roots out of the denominator.
@XBQV0
@XBQV0 3 жыл бұрын
I really gotta work on my geometry, all these Geometry problems on KZfaq are so interesting!
@MaxMathGames
@MaxMathGames 3 жыл бұрын
This is easily, one of the easiest questions on your channel but I still love your videos. ,👍👍👍
@katherinegaymes
@katherinegaymes 3 жыл бұрын
suggestion for a future problem: can this be generalized to n number of squares?
@hydraslair4723
@hydraslair4723 3 жыл бұрын
Yes! Notice that the leftmost bit of the base which is not covered by the squares is always a/√3 in length by trigonometry. Likewise the rightmost bit will be na/√3. This means that one must just solve the equation: a/√3 + a + 2a +...+ na + na/√3 = 1 Which just gives: a = √3 / ((1+n) + √3(n(n+1))/2)
@ChrisWEarly
@ChrisWEarly 3 жыл бұрын
Rearranging the fraction at the end is at first confusing since you move all the signs. It looks wrong and would’ve been nice if you explained how you did it.
@suhnshaiene
@suhnshaiene 3 жыл бұрын
Practice with simpler numbers, it's a very handy trick to know www.desmos.com/calculator/mxobfpdapz
@JoseFernandes-js7ep
@JoseFernandes-js7ep 3 жыл бұрын
He just multiplied both numerator and denominator by - 1.
@opeyemiladeji2759
@opeyemiladeji2759 3 жыл бұрын
@@JoseFernandes-js7ep is that legal
@KevinLarsson42
@KevinLarsson42 3 жыл бұрын
@@opeyemiladeji2759 it is actually
@ellisk6171
@ellisk6171 3 жыл бұрын
Yea I was confused about this but I get it know
@chilling00000
@chilling00000 3 жыл бұрын
Hi Michael, I have an interesting problem. Inside a unit square (side length is 1), is there a point whose distance to all 4 vertices are rational ?
@daveturner5305
@daveturner5305 3 жыл бұрын
1=a+2a+3a+x+3x (x being as described in the video & 3x by similar triangles) x= a/tan(60)=a/sqroot(3) 1=6a+4a/sqroot(3) a=1/(6+4/sqroot(3)) 0.120 to 3 decimal places simples!
@lontonk13
@lontonk13 3 жыл бұрын
Now i understand what gura's "a" means
@nappy6969
@nappy6969 3 жыл бұрын
I didn't know that apex predator uses maths too
@kholosimp
@kholosimp 3 жыл бұрын
Oh wow. Did not expect a shrimp here :D
@nappy6969
@nappy6969 3 жыл бұрын
@@kholosimp we are shrimps
@RazanAr51
@RazanAr51 3 жыл бұрын
Ah yes, another man of culture who also likes math
@OtakuOne
@OtakuOne 3 жыл бұрын
I was looking for this comment. Shrimps unite.
@Invalid571
@Invalid571 3 жыл бұрын
Very interesting and fun problem. :) I have a new question for you which I couldn't solve. It was on my latest Newtonian mechanics exam and it was listed as a question with a short answer i.e. it was considered easy. I hope you can help me because I have no idea how to solve it. Here goes: Which of the following differential equations systems have periodic solutions: a) x' = y y' = 3x^2 - y - y^5 b) x' = y y' = x^2 + y^2 + 1 c) x' = y y' = (x^2 +1)y - x^5
@giuliosf
@giuliosf 3 жыл бұрын
The a) and c) have the solution x=0, y=0, which are periodical. The b) i don't know if there are ones, but surely not constant (easy to check)
@Wurfenkopf
@Wurfenkopf 3 жыл бұрын
Well, in order to be periodic a solution has to be limited, which leads me to believe that the answer is (a). By the way, it seems that there are multiple solutions since (a) and (c) both admit the constant solution x=0, y=0. Maybe you're looking for a system that has ONLY periodic solutions?
@Invalid571
@Invalid571 3 жыл бұрын
@@Wurfenkopf If I recall correctly the exact wording of the question was: "Which of these d.e. systems have periodic solutions? Justify your answer shortly."
@Wurfenkopf
@Wurfenkopf 3 жыл бұрын
@@Invalid571 Well then, my answer would be "(a), because the others have at least one solution that grows exponentially"
@KirbyTheKirb
@KirbyTheKirb 3 жыл бұрын
Really nice problem, perfect for me, easy to follow and understand.
@JLvatron
@JLvatron 3 жыл бұрын
Nice puzzle! I solved it just like you, but not so elegant. I didn't use sqrt (3) and I used a calculator to completely decimal it.
@Sombres
@Sombres 3 жыл бұрын
question: what is a gawr gura: "i happen to be an expert on this subject"
@pettanshrimpnazunasapostle1992
@pettanshrimpnazunasapostle1992 3 жыл бұрын
Also gura:20-11=?
@hourglass2836
@hourglass2836 3 жыл бұрын
I never knew I'll encounter the VTuber rabbit hole in a maths comment section
@aluiziofjr
@aluiziofjr 3 жыл бұрын
6:08 Wasn't the denominator supposed to be negative?
@lalityamarathe1533
@lalityamarathe1533 3 жыл бұрын
You're right! but actually even the numerator becomes negative. So he just changed signs of both numerator and denominator (multiplied both by -1) and tadaa! You're done!
@vuvu7005
@vuvu7005 3 жыл бұрын
He multiply by -1
@anshumanagrawal346
@anshumanagrawal346 3 жыл бұрын
Wow! This is actually relaxing
@zooboor8148
@zooboor8148 3 жыл бұрын
So amazing.
@someone-rr7fz
@someone-rr7fz 3 жыл бұрын
'a' is smol shark
@mamoopy
@mamoopy 3 жыл бұрын
chumbuds
@sachikamankai
@sachikamankai 3 жыл бұрын
a
@jacob_himilton
@jacob_himilton 3 жыл бұрын
Everywhere I go
@Aizze_R
@Aizze_R 3 жыл бұрын
Gura: a Hololive : a KZfaq Recommendations:
@OtakuOne
@OtakuOne 3 жыл бұрын
a
@brendanward2991
@brendanward2991 3 жыл бұрын
3:43 - That's actually a good place to stop.
@BlurbFish
@BlurbFish 3 жыл бұрын
Why do you think it is a good idea to stop before the question has been answered? You're asked to find a, but the expression at 3:43 is still one or more steps away from being that - it's like selling raw dough and calling it bread.
@brendanward2991
@brendanward2991 3 жыл бұрын
@@BlurbFish Because the rest is just elemenatry algebra. He should have said: "And I'll let you simplify this result yourself. And that's a good place to stop."
@BlurbFish
@BlurbFish 3 жыл бұрын
@@brendanward2991 Solving a system of two equations with two variables is also just elementary algebra, so by that logic you might as well stop even earlier. The problem very explicitly asks you to find A - the final answer to such a problem would be "A is [an expression for A]", but the suggested expression clearly does not work for that. If a construction foreman needed three pieces of steel with lengths a, 2a and 3a, do you think he'd be happy to receive the expression at 3:43 as a result? (yesyes, I know in that latter example there'd be additional work with tolerances and significant digits)
@Grizzly01
@Grizzly01 3 жыл бұрын
@@brendanward2991 What a dumb outlook. If you haven't written down an expression in the form 'a = some number', then you haven't provided a solution to the problem.
@M235i_bluelightning
@M235i_bluelightning 3 жыл бұрын
I love geometry so much. Thank you for interesting video.
@RAJSINGH-of9iy
@RAJSINGH-of9iy 3 жыл бұрын
Can you help me with this? Any positive integer n can be written as (a 1) + (b 2) + (c 3) uniquely where 0
@TechnolightGT
@TechnolightGT 3 жыл бұрын
Not gonna lie I was expecting Gawr Gura's A
@bradleywalker6033
@bradleywalker6033 3 жыл бұрын
Wait why didn’t he make the 276 negative in the second to last step. Or am I just trippin
@_modernmage
@_modernmage 3 жыл бұрын
He didn't make 276 negative because he multiplied the numerator and denominator by -1, he just didn't say it. If you check, the 12sqrt(3) is now being subtracted from 54, not the other way around. Just makes the fraction look cleaner!
@brandonfaddis7443
@brandonfaddis7443 3 жыл бұрын
@@_modernmage but wouldn't that give you -a instead of a?
@anuraagsonu6016
@anuraagsonu6016 3 жыл бұрын
@@brandonfaddis7443 He has taken minus both on the denominator and numerator which is same as not having minus up and down as they would just cancel off.
@_modernmage
@_modernmage 3 жыл бұрын
@@brandonfaddis7443 it's doing *(-1/-1). Multiplying something by x/x gives you the same thing, its just a different way of formatting it. It's the same thing he does to rationalize the denominator
@dmitrygrv5661
@dmitrygrv5661 3 жыл бұрын
The numerator of the fraction is also negative
@trex9966
@trex9966 3 жыл бұрын
For generalized n number of squares a=(6n-4sqrt(3))/(3n^3+n^2-4) I dont think it can be simplified further
@SafetyBoater
@SafetyBoater 3 жыл бұрын
I like that the method you used to take 48 from 324 was the same way that I do my calculations mentally.
@muckchorris9745
@muckchorris9745 3 жыл бұрын
TBH: The nicest description of the number is the exercise to solve it.
@adrianbradicic8039
@adrianbradicic8039 3 жыл бұрын
Just as I thaugt I whould like trigonometry in high school...
@rakebluewallgaming6185
@rakebluewallgaming6185 3 жыл бұрын
Looks like you need english
@colintruran3976
@colintruran3976 3 жыл бұрын
I got a stroke from this
@2false637
@2false637 3 жыл бұрын
Simple yet fun!
@fredfrancium
@fredfrancium 3 жыл бұрын
Amazing teacher
@barbadosslim4044
@barbadosslim4044 3 жыл бұрын
He sounds exactly like benson from regular show
@user-pj9fm4zh4v
@user-pj9fm4zh4v 3 жыл бұрын
A question similar to this appeared in the latest entrance exam of Nada Junior High School in Japan.So, I've already known how to solve this problem.
@kanewang316
@kanewang316 3 жыл бұрын
I wonder how I can get your shirts you showed in the end of this video if I live in Taiwan. Please tell me.
@MattiLargeWorld
@MattiLargeWorld 3 жыл бұрын
This was indeed vey relaxing
@wagsman9999
@wagsman9999 3 жыл бұрын
Me: "Yoda, what do think?" Yoda:"The math is strong in this one."
@frankineskinecense
@frankineskinecense 3 жыл бұрын
"a" is the first letter of English Alphabet.
@irisinthedarkworld
@irisinthedarkworld 3 жыл бұрын
oh neat. you learn new things every day
@Birol731
@Birol731 3 жыл бұрын
good question, thank you very much 👌
@crimsonfist1408
@crimsonfist1408 3 жыл бұрын
quality video. short and sweet!!!!!!!!!!!! worth a sub
@brendanfan3245
@brendanfan3245 3 жыл бұрын
This one is primary school level compared with your other Olympiad problems.
@allpeopleon
@allpeopleon 3 жыл бұрын
So easy for Russian 9'th class
@mafincornot5475
@mafincornot5475 3 жыл бұрын
Ha-ha, Hello! (Рекомендации объединяют)
@mafincornot5475
@mafincornot5475 3 жыл бұрын
@@acordeon3000 Yes, so Neil DeGrasse to was asked about the stupidity of American students
@Ig0rms
@Ig0rms 3 жыл бұрын
I'm in med school and I really don't know why am i here. But loving those videos. Hugs from Brazil.
@michak8029
@michak8029 3 жыл бұрын
watched only like 5 videos on this channel and this is 1st puzzle I knew how to solve straight away xD
@mandrewsvideos
@mandrewsvideos 3 жыл бұрын
Nice problem, overly complicated solution. tan 30 is about 0.58, so multiply 0.58 by 4 to find the missing a's on the base of the triangle. Add this to 6 and take the reciprocal. 1/(4tan30+6)
@hellen-pg9lu
@hellen-pg9lu 3 жыл бұрын
this should've be relaxing but i don't understand a thing (;´༎ຶٹ༎ຶ`)
@arindamkashyap9420
@arindamkashyap9420 3 жыл бұрын
So.. you aren't a maths student right? 😶 Otherwise I'd be worried for you
@leonardoleano627
@leonardoleano627 3 жыл бұрын
Could you make the same problem more generical imputing a n number of squares. What would be the answer?
@malawigw
@malawigw 3 жыл бұрын
Gonna do this with my Class next week!
@leonardokeller5254
@leonardokeller5254 3 жыл бұрын
Nice job, although the problem is a bit too easy... Don‘t get me wrong but I came up with the same idea within 10 seconds of thinking and the rest would have been easy simplification. I‘m sure you are a bit inspired of the Chanel „mind your decisions“ and I mean you are showing us your face and it is a bit more funny, yes, but the problems are a bit too easy. However, Cool videos and I hope that you will reach quickly 100k and when this is done I‘m certain that you will reach more milestones. Have a nice day Best Regards
@Kneal911
@Kneal911 3 жыл бұрын
too easy? at some point in your life you werent able to solve this problem. See that he is teaching how to solve it for free.
@whozz
@whozz 3 жыл бұрын
I just found another solution, a = a
@davidbrisbane7206
@davidbrisbane7206 3 жыл бұрын
Or 1 = 1, unless a = 0 lol.
@klausolekristiansen2960
@klausolekristiansen2960 3 жыл бұрын
Is there some way to get to see the answer? Can the logo that covers it be removed?
@perrydimes6915
@perrydimes6915 2 жыл бұрын
I think it is more aesthetically pleasing to consider what is the value of x, when n is the number of squares. In that case, x = 1/(1+ n)(1+ nα) Where α = tan(pi/3). This makes it easier to generalize to any value of n or any isosceles triangle, as this depends on both n and the tan of the angles. Great problem and video.
@ReynoldSparkton
@ReynoldSparkton 3 жыл бұрын
I missed the point that, at which point this problem was supposed to be relaxing?..
@jacobkaiser9080
@jacobkaiser9080 3 жыл бұрын
point: unbounded
@julesvg3111
@julesvg3111 3 жыл бұрын
What is a? Baby don't hurt me Sorry I didn't actually watch the video
@qqpit1
@qqpit1 3 жыл бұрын
Similar triangles allows you to conclude that a = x*sqrt(3) without trig. Also, I think doing the other substitution (so you solve 4x + 6x*sqrt(3) = 1) is a little bit neater and gives a slightly simpler answer with less work: a = sqrt(3) / (4+6*sqrt(3))
@sammylatino381
@sammylatino381 3 жыл бұрын
A = 1/(6 +4tan(30)) Simplest form i could get it to. Doing a little trig to get the bottom distance of the left and right triangles, (left being tan(30) and right 3tan(30)) add them together with 6 then divide 1 by that total. I’d say it’s the quickest route but the fact that there’s more than one way to a correct answer is the beauty of math.
@SeekNKnow
@SeekNKnow 3 жыл бұрын
not relaxing when he mispronounces equilateral constantly.
@kenhaley4
@kenhaley4 3 жыл бұрын
Yay! I got this one!
@rahulranjan9151
@rahulranjan9151 3 жыл бұрын
Very helpful sir
@ravraid
@ravraid 3 жыл бұрын
Fun problem and good explanation. One nit: the graphic in the thumbnail image isn’t right. The sides of the 3a box are 2x those of the 2a box.
@duckduckbobo5208
@duckduckbobo5208 3 жыл бұрын
I solved by using 30 60 90 to find the lengths of x (a/√3) and 3x (a√3), then adding the whole side together.
@Olpaj
@Olpaj 3 жыл бұрын
I fucking love this channel. I wish they used colored chalk in my maths classes at school. I'm not even particularly involved with math on a daily basis, besides calculating which brand of pizza offers more area for the money.
@svetievboris
@svetievboris 3 жыл бұрын
I have a question: given that 4x+6a=1 doesn't it mean that x=a since for example 4×0.1+6×0.1=1 ? I have very little knowledge of math and even the math in this video is hard for me to follow, considering this please help me understand if my assumption above is wrong and if yes then why is it wrong. On the other hand if it is right then why is all the math manipulation shown in this video actually necessary? Thank you.
@takyc7883
@takyc7883 3 жыл бұрын
pretty proud tha i worked this out :)
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