Paraboloids and The Building which Set Things on Fire

[@Zaurthur]

Biggest problem I've had in any math class is lack of interest by the instructor. NO SUCH ISSUE HERE. got to love it

[@thedave7760]

+1337penguinking I have never understood equations and algebra but that was so well explained I almost got it, well about 75% of it. not sure what I would use it for but it's good to understand new concepts. New to me any way. I might have stood a chance if he was my 10th grade math teacher.

[@jacksainthill8974]

+The Dave Well, at least you seem to be among the 37% of people who have managed to understand percentages. Unfortunately, the other 91% just make idiots of themselves whenever they try to use them.

[@RalphDratman]

+Laurelindo But students usually look that way too as the end of the semester approaches. Math is fun when exploring but can get boring if one is just plowing through material to pass a course. I find it horrifying to watch a class where both teacher and students seem to have turned to stone.

[@sarahszabo4323]

+Jack Sainthill No, no, no, you have it all wrong. EXACTLY 11/10 (110% of all people) of people have trouble with fractions and percentages.

[@ahyessmoxersarehere6905]

Profile picture is a blast from the past... WAIT 6 YEARS AGO

[@mihauinfamous]

"When life gives you lemons, scorch them."

[@ConductiveFoam]

+mihauinfamous Am I wrong in thinking about combustible lemons and giving lemons back right now?

[@RDSk0]

+nHalbleiter It seems that Matt had worked in Aperture Science at some point and got a combustible lemon that burns your house down.

[@screwaccountnames]

+KinRedysko *that gets burnt down by your house, in this case.

[@mudkip_btw]

Now that's a life quote I'd use

[@khorps4756]

DEMAND TO SEE LIFE'S MANAGER, MAKE LIFE RUE THE DAY AND THOUGHT IT COULD GIVE CAVE JOHNSON LEMONS!

[@reDustt]

Love these laid back proofs, and an assumption of basic calc was a pleasant surprise for youtube!

[@standupmaths]

I go about life in the blissful belief that everyone knows basic calc. I am often proven wrong.

[@julespoon2884]

+standupmaths I made this simulation for a project about a year ago, regarding this issue: www.desmos.com/calculator/uwtgzdcyqw Play with f(x) and change the angle. Consider: www.desmos.com/calculator/dl0thjohpp One day, I will make a mirror that shape and make my dream come true.

[@cryptexify]

+standupmaths YOU don't even know basic calc, Matt -__- You didn't know the alternating harmonic series is equal to ln(2).

[@julespoon2884]

cryptexify Hm... that is a rather boring topic to present in youtube.

[@TrimutiusToo]

+standupmaths well some people do know it. For me it was like. Come on, proof takes too long, derivative of a quadratic formula is an obvious thing, no need to spend so much time on something so simple =) well though if I would explain it myself I would do the same, so sorry for being hypocritical... =)

[@phase623]

*bursts into flame "yes!" *slower burst "yyeess!!" *slowerer burst "YEEEEEEEEEEEEEEEEEE-"

[@alexwang982]

T

[@alice_in_wonderland42]

YEET

[@jttnc]

Favorite part of the video

[@ze_rubenator]

To me, a Norwegian, the fact that satellite dishes are paraboloids is quite intuitive. It might have to do with the fact that our word for _sattelite dish_ is _parabol_. Just thought you'd like to know (:

[@juggernaut93]

+Ze Rubenator Here in Italy we use "parabola" or "antenna parabolica" for satellite dishes :)

[@SKyrim190]

+Ze Rubenator Portuguese it is "antena parabólica". Quite often people will drop the antena part and just call them "parabólica"

[@somitomi]

+Laurelindo Same in Hungarian: parabola + antenna = parabolaantenna. Both words being loanwords (especially ones with the same spelling as in English) made this super simple, at least in writing.

[@proefslak]

In the Netherlands, it is called a "schotel". That word is also used for large plates and for saucers.

[@tjimicole2677]

+Laurelindo They truly do live in the future in Sweden.

[@SixFootDog]

Someone made combustible lemons. Cave Johnson would be proud.

[@01cton]

Legoman6157 underrated comment

[@mitzapper2]

IM THE MAN THATS GONNA BURN YOUR HOUSE DOWN WITH THE LEMONS

[@avisian8063]

Criminally underrated comment!!!

[@0ia]

@@avisian8063 It's been so long that I don't think that the comment is criminally underrated.

[@Bubu567]

Citric acid is flammable. Lemons are full of citric acid. Combustible lemons isn't such a strange thing after all.

[@NoriMori1992]

"You're in London. You're out taking your lemon for a walk." That sounds like an opening to a great interactive text adventure webcomic. XD

[@Maukustus]

standupmathadventures

[@erniesulovic4734]

Sherlock Holmes could solve this case in mere seconds

[@alexandermcclure6185]

this got me dying laughing omfg especially bc this seems like what I might do in Britain 🤣🤣🤣🤣

[@lesboarders]

13:40 Chalk on a blackboard is a fantastic sound! It was a very sad day when my Maths department replaced them with fancy whiteboards and projectors, they were the only thing that persuaded me to offer solutions in lectures.

[@connortremblay1259]

I was experimenting with parabola and may have accidentally blown up a light bulb. The fun part was how my face was about 5 inches away. A real parker square on my part

[@MonsieurOuellet]

11:03 - > Keep that in mind ladies. If you want the d, start with the gradient of the tangent.

[@anna-graceschumann8869]

I'm dating a mathematician. This is important

[@Bcmwolverine]

Hey Matt I showed this in my science class and my teacher was really impressed and my classmates laughed a lot at the lemon part. Keep up the amazing videos!

[@lukeherring9464]

Having been told, when I was younger, that this kind of stuff is supposed to be boring, I'm grateful to have found this!

[@ELYESSS]

I watched until the end, think I need to subscribe

[@MeAgain998]

+ILYES Same.

[@OriginalPiMan]

+ILYES No! Join me in non-subscription and fight the power! Disclaimer, there is nothing to gain by joining me.

[@cameodamaneo]

11:03 "To get that d" Everyone, take notes.

[@goneutt]

The windows were aligned to the parabaloidal architecture, but can be detuned to actually be flat wrt the street. It's a tweak engineers have had to invent to save architects for decades.

[@EliCarlton]

13:40 was a little nugget of gold. The sass came from no where and I appreciate that.

[@htasul]

Pfft this is so fake - we don't have sun in Britain

[@wea69420]

it will reflect rain and soak your lemon!

[@fisch37]

@@wea69420 Assuming your rain is hail and indestructible (so hail in North-Rhein Westfalia) , yes

[@mistec34]

I love your enthusiasm and willingness to explain in the simplest terms possible without losing the meaning. Keep up the great work! :)

[@CodeWeaver]

Every mathematics teacher should be this enthusiastic. I was lucky enough to have a pretty good math teacher, but it surprises me not one bit that so many people not only struggle with it, but then failing to get help and see this level enthusiasm, write it off from their list of things they want to have in their brain. Keep up the enthusiasm/

[@pigeonlove]

This is a 15 minute video...

[@PetarKaser]

I like your charisma, instructions are clear... Video 10/10 audio 10/10 please never stop making these. You and that other numberphile guy... Wow

[@ReverendTed]

It wasn't until this year that I appreciated that "trigonometry" is literally "the study of trigons" or, as we know them now, "triangles".

[@Moingboy]

Well... because it uses "metry" it's probably more literally the writing of trigons. And to my understanding, at least from what I remember from long ago, a trigon is less limited in its definition. (Something about one of my teachers calling a triangle with curved sides a trigon)

[@eideticex]

Trigonometry. Trigon, Metry or Measure. The study of measuring triangles.

[@seraphina985]

+Moingboy As Alan mentions -metry is to measure, the suffix for writing is -graphy from ancient greek gráphō, latin -graphia, french -graphie to the engilish -graphy to write. Thus words like calligraphy, cartography, biography, photography

[@deeelmore4560]

Seraphina S pornography

[@anisometropie]

16:05 thank you matt, this simple and yet powerful act of recognition and appreciation, and that feeling of belonging the arises from it. Belonging to the same species of math nerds. You make me want to embrace and accept fully that part of me that was always there, and make me want to express that nerdiness shamelessly - I have always felt compelled to hide rather to fully accept who I am - You are an inspiration, And being able to talk about maths, making it accessible and even an attractive subject, is quite an achievement.

[@engelsteinberg593]

Except that like math is no being "nerd".

[@unvergebeneid]

"Loss of generality" nice :)

[@unvergebeneid]

Also pretty sad though. I've never before seen generality being lost. People always assure me this wouldn't happen.

[@standupmaths]

+Penny Lane It's ok, we managed to pick-up generality again!

[@alcesmir]

+standupmaths You dropped the trivial case x=0 in the proof when playing with tan, so some generality was indeed lost on this very sad day.

[@robin888official]

+Alcesmire Actually the proof also misses x=1/2, when Θ=π/4 and tan(θ) = 1. In that case calculating tan(2θ) leads to division by zero. ;-)

[@alcesmir]

+Robin Koch The singularity at x=1/2 is quite meaningful though, since inverting it gives the correct slope (1/inf=0). In a sense the same applies at x=0, since tan(θ)=0 implies tan(2θ)=0 (from periodicity) and inverting that gives you ±inf depending on the limit you choose. I think a more proper mathematician would scoff at both of those (ab)uses of infinity, albeit being technically ok.

[@sneakerboots]

I used this video to teach my 9 year olds about the usefulness of paraboloids! (only the first half, the Math is too complex). I love how you introduce these concepts! Please tell me how to finance more of your videos!!!

[@standupmaths]

I'm glad the videos are useful! They can come back for the proof when they're older. I'll be asking around for support soon, but at the moment I'm getting by with old equipment I already own and small amounts of free time. Stay tuned!

[@connfdm]

"accidentally curved in a certain way" How do you know it's accidental? What if it's an evil alien who came to Earth to sabatoge all of our lemons?

[@fisch37]

Pretty sure they'd target the cabbages

[@j.hawkins8779]

Adorable pfp

[@NoNameAtAll2]

every villain is lemons

[@avananana]

The enthusiasm in this channel reaches the sky. I love it haha.

[@jetstreamjackie3437]

The sound chalk makes is satisfying! I have no idea what you're talking about.

[@Cream147player]

Well that was one of the best videos I've ever watched on KZbin. Suck us in with the fun premise and then the basic explanation, chuck in an explosion, hit us nerds with the proof, with a beautiful ending to that proof that fits the whole thing together all interspersed with great comedy throughout. That is factual entertainment at its finest.

[@KarlFFF]

That curvy action kept me focused all the way to the end.

[@jkid1134]

Thank you so much for doing this proof! It was a step or two up on the rigor from the typical videos here (and so much more on numberphile), and as someone who enjoys actually seeing and proving the math rather than talking about it, it was a great breath of fresh air.

[@dan339dan]

"I highly recommend deriving the formula. It's good fun" said Matt. I'm writing my secondary education exam the next month. I can assure you I hate proving LHS trigonometry = RHS, because there are many formulae to choose from and there are dead ends.

[@standupmaths]

Yes, and trig formulae are surprisingly easy to break with the wrong domain/range. I skipped right over when x=0 for that very reason…

[@dan339dan]

standupmaths It would be fun doing them not timed though :) I just hate myself when I skip them in the exam thinking I wouldn't have time just sitting there checking every steps and know that if I saw the solution, I would totally understand the thinking process. I guess I need practice?

[@purplezart]

+standupmaths isn't the x=0 case fairly trivial anyway? tangent slope at 0 is 0, so the beam reflects at an angle of 0... am I missing something?

[@wilddogspam]

purple zart one year late, but you're missing that there's no one y intercept or d to be found at 0. Both tan(0) is undefined and he explicitly removed it from the algebra side when he asserted that 4x/4x = 1, which is only true for x ≠ 0.

[@_noirja]

As a long-time Brady's countless channels viewer, surprised I've somehow missed your channel! Brilliant stuff, I love your humorous teaching style :P

[@timothy9958]

this was fun, I feel like I don't get to watch people work out slightly complicated math problems anymore.

[@flyingoctopus221]

I love your videos Matt. I genuinely enjoy your enthusiasm for math(s) and whether you realise it or not you are helping nurture my future in math by making these videos.

[@JamieThelin]

I was just about to demand a proof

[@standupmaths]

I hope you're happy then!

[@JamieThelin]

standupmaths certainly, awesome video as usual :)

[@Giddefication]

Hey Matt great video! Your enthusiasm is contagious!

[@novajohansson3194]

In Sweden, a satellite dish is actually called a "parabol".

[@anitejbanerjee2278]

Thank you very much, Mr. Matt! I find your videos simply amazing and you inspire me to go beyond what I know. I already knew differential calculus (and some of Integral Calculus), but you have been teaching me that it's also about getting your hands dirty in the nitty gritty of Mathematics and having a good time, rather than merely learning out of the book (which I can not undersell, but I hope you get the point!). True "Mathematical" thinking comes from solving problems and thinking about them in abstract ways, which seems tough to me right now, but I hope it shall get easier as I spend more time doing so! Once again, thank you very much!

[@LegitToaster]

Combustible lemons. Portal anyone?

[@ck7671]

man, I couldn't get any sleep because I couldn't get to this conclusion. I'm really thankful, t's way funnier to look at you on a black board than reading for it in a sober well-documented piece of paper

[@DanielVidz]

Perhaps do a video about retroreflectors.

[@standupmaths]

That's a good idea. I love the 'cat eye' reflectors used on roads.

[@egeatilla5308]

I've never been so excited waiting for the climax of a proof

[@rosieisla8286]

Where did the lemon go at 1:12?

[@gownerjones2]

+Rosie Isla Not sure if you want an accurate answer but my best guess is that the lemon wasn't actually there. He edited that in with some clever motion tracking and made it poof away at the right moment.

[@rosieisla8286]

+HOLyPumpgun | Gaming Hmm, maybe. I would say something like "Wouldn't that be a lot of work?" but it's Matt Parker and he isn't known for doing stuff the easy way.

[@BlobVanDam]

+HOLyPumpgun | Gaming I think the lemon was real, and he actually just dropped it, and covered it up craftily with the explosion and a bit of editing.

[@YourMJK]

+HOLyPumpgun | Gaming Much much simpler: It was a real lemon, he just dropped it and hid the falling lemon behind a black bar he edited in later

[@gownerjones2]

YourMJKTube That would make sense, except his hand is in the way. So unless he has a perfect image of his own hand in that position, that wouldn't work. You'd see the lemon fall in front of his hand and then disappear in the black background. And besides, it's actually not very difficult to motion track a few seconds of video like that. He may just have done some frame-by-frame keyframing as well, who knows.

[@SapientPearwood]

for a fairly trivial bit of geometry, that was a satisfyingly rigorous proof. I especially liked the general lack of hand holding. Its nice when a youtube video about math assumes that you might actually know some math going in.

[@gunar.kroeger]

he should be next doctor who

[@spidercollector9636]

Doctor. Not Doctor Who. The Doctor, say it with me, THE Doctor.

[@kjono4611]

Gunar Kroeger surely he'd be too busy talking about spreadsheets and proofs to finish an episode though

[@lawrencecalablaster568]

This is so awesome! :D I love weird architecture & mathematics & history. Thank you for making this video!

[@damo2353]

Nice video. Maybe if you had been my Math101 lecturer I might not have ended up as a lawyer.

[@stefan_munzi7530]

The small special effects like the disappearing of the lemon at the beginning are so awesome :D

[@achtungcircus]

There was (is) a solar oven in southern France using exactly this concept.

[@rosieisla8286]

In one of my schoolbooks it also has an example of cheap solar ovens made with tinfoil in poor countries. Apparently it works really well, because a lot of poor countries are located at the equator.

[@rich1051414]

+Rosie Isla The nice thing about them is the larger you make them, the more powerful they become, and the larger you can make the focal point(which is the actual oven). Since you can literally make them out of garbage, that is a really powerful thing for people in any country to learn.

[@finbob08]

+Richard Smith however, the parabola has to be extremely accurate for each day to reflect to the focal point

[@finbob08]

ray

[@flaminghat1739]

Going through precal classes now. personally It is a lot of fun. thank you for doing videos such as these. Sometime this is all I need to stay intrigued. I love and very much miss the sound of chalk on a chalkboard!!!!!

[@hectors03]

who doesn't like chalk board?? much more fun.

[@stormsurge1]

It smells really bad

[@ze_rubenator]

+kkarahodzic wat?

[@obink3245]

+Hector Rodrigues I hate the feeling of chalk in my hand, it just feels so strange.

[@zmail8566]

14:00 "we're sorry for your white boy ears"

[@sk8rdman]

+Hector Rodrigues I wouldn't say I'm opposed to chalk boards, but I'm generally in agreement that dry erase boards are better. Chalk is messy, dry, and some people have an allergic reaction to it. I can appreciate the nostalgia of a chalk board, but at the end of the day, I'd rather use dry erase in almost every case. However, in both cases, one should always use the appropriate equipment to erase. Wiping down either type of board with a bare hand is a good way to ruin it.

[@dlrosbury]

You got me Matt. I watched until the end and so, feeling compelled, I subscribed. BTW, I don't need a proof, I WANT a proof!

[@MuradBeybalaev]

Life is like riding a bicycle which is on fire, and you're on fire, and everything is on fire and you're in hell.

[@jeremyashford2145]

By placing a light source in the point of focus a paraboloid may also be used to spread light evenly over a calculated area. Holophane have been producing highly efficient prismatic reflectors for over a century in England, France, and USA.

[@lare290]

To be honest, I love chalkboards more than whiteboards. the sound of the chalk (when used correctly) is so satisfying.

[@kalebbruwer]

but the powder is irritating and most teachers properly clean the thing only once a year so it's a big mess.

[@alexeysaranchev6118]

They're making the pupils clean the board here. "Who is on duty today?" used to be the basic English line everyone knew along with "London is the capital of Great Britain"

[@frantisekzverina473]

PerunaVallankumous indeed, and the squeaking of the whiteboard markers is just pure evil

[@alexkatz9047]

Obviously only russian pupils have that tradition.

[@Momo40K]

I firmly agree!

[@joshuathomas6423]

I have absolutely no idea what you just said, but it looked really awesome!

[@petermarsh4578]

I don't care about the maths, but how the hell did he vanish that lemon at 1:12?

[@satchmo1991]

He drops it, replaces it with the fire effect, and masks it as it falls out of frame, I am fairly certain.

[@wurttmapper2200]

Satchmo1991Music I thought the same thing

[@pedroespino6988]

Thanks Matt Parker. YOU ARE THE BEST. YOU MAKE MATH LOOK EASY.

[@EUPassionStorm]

"To get that D..." Beautiful quote

[@mennoltvanalten7260]

Bike lights are often made with paraboloid shape, so the light source shines light more straight towards the front, letting the light reach further.

[@dolantremp]

"to get that D we have to start with the gradient of our tangent"

[@stumbling]

Mathematics: the art of doing nothing and still getting it done.

[@tomahwakthehawker8725]

Matt I love you so much that I clicked the advert adjacent to the video (wait for it) 3 times!

[@smmoom1212]

COMBUSTIBLE LEMONS!!! GODS MAN CAVE JOHNSON ACTUALLY DID IT!!!!

[@DemolitionTurtle]

Ha ha, loved the video, Matt! I'm really glad to see you still making lots of regular videos; I hope this continues as they are always a joy to watch :)

[@standupmaths]

I'll keep making them as long as I have the time!

[@LemonChieff]

I'm not sure how I feel about this. ._.

[@TauGeneration]

To get that D..

[@relwoodmusic3630]

I don't understand 80% of the math, but I still enjoy watching for some reason. Great work!

[@drumset09]

Ha, jokes on you Matt. I watched the entire thing and didn't subscribe!

[@alexeysaranchev6118]

Me too. Because I was already subscribed.

[@fisch37]

@@alexeysaranchev6118 :o

[@larskruse7575]

@@alexeysaranchev6118 well you could have desubscribe and resubscribe again

[@toomdog]

I wasn't already subscribed, but I am now. I've been watching and enjoying your videos for years; I even tie my shoelaces more efficiently now thanks to you.

[@guydht1]

WHY ARE THERE 4 ARROWS IN 7:30 INSTEAD OF TWO YOU CAN'T SAY WHAT'S THE POSITIVE DIRECTION THAT WAY AHAHAHAHAH

[@danielpare9129]

+guy hircshorn I think they are infinite answers to that question.

[@jeffc5974]

+guy hircshorn The arrows don't indicate positive, they indicate a continuation. Continuations can go both positive and negative.

[@Poldovico]

+Jeff C Arrows can indicate continuation? I always thought they just indicated orientation, and continuation would be indicated with dots if it were indicated at all as opposed to just assumed to be clear.

[@jeffc5974]

Poldovico Math is different from english.

[@Poldovico]

Jeff C I'm sorry, I don't understand what you mean by that.

[@JohnCharter]

Here in the states, as I'm sure you're aware, we recently had a huge lottery jackpot. Not long before, you did a couple videos on probabilities of winning the lotto. Combining all of this and the joy each of your videos brings to me, should I ever come into such an amount of money, I would throw (literally if needed) unimaginable offers at you to relocate and become my personal tutor. I'm not even in school, but I would enroll for the cause.

[@vasudevans1224]

Already there in sixty symbol poor Matt Brady always beats you

[@standupmaths]

Really‽ Honestly, every time…

[@lylium6830]

+standupmaths Nice use of the interrobang there Matt! It makes me happy to see someone using it :D

[@vasudevans1224]

+standupmaths the first time to my knowledge being the Valentine's Day one

[@sabaca304]

Im used to these boards. We use them mainly in my school. How did you know I was subbed, that's magic!

[@electromika]

Mmm, pyromania.

[@Meb8Rappa]

+Sulthan14 Pyraboloidmania

[@slendy9600]

+Meb8Rappa well done

[@RainBoxRed]

13:46 we love the sound. More black/green board maths please.

[@alfonshomac]

hahah yup, already subscribed.

[@No0dz]

It is so satisfying to watch a proof that requires nothing but basic calc and trig. It's stuff like this that makes me want to go for a PhD 12 years after getting my Master's

[@ardenvarley-twyman8352]

Whiteboards > Blackboards.

[@MysteryHendrik]

brown paper > whiteboards

[@dubleeble]

+MysteryHendrik Low Latency Pen Tablet > brown paper

[@SpySappingMyKeyboard]

+Leafy is Beefy Stone tablets > Low Latency Pen Tablet

[@gregbernstein7524]

+Arden Varley-Twyman Get outta here you young whipper-snapper!

[@jja77a]

+Arden Varley-Twyman Racist!

[@skellious]

I wish you'd been my maths teacher at school! I still did okay in maths but I didn't end up going into a career in it. But now I'm learning a lot from you and the numberphile guys and maybe one day I'll actually take some higher level maths courses and get my maths to where it could have been :)

[@standupmaths]

It is never too late to learn maths. And it makes for a great hobby.

[@Kieran-4]

I can't believe the guy that gets annoyed at 'incorrect' snowflakes is making videos so regularly

[@standupmaths]

I can't believe the guy who got annoyed that I got annoyed at inaccurate snowflakes can't believe that.

[@ebgamer29]

I watched this video over a year ago. Three months ago I started (and yesterday I finished) a study abroad at qmul. I am amazed at how much of London I had forgotten about from this video 😂

[@Acleron]

Always a beautiful proof when it finally simplifies. Thank you for that.

[@theKKCD]

Thanks for the great video Mr Parker was very entertaining to watch!

[@Laftel]

Here in Brazil, satellite dish anttenas are called parabolic antennas(antenas parabólicas), as almost everyone has them and we needed to separate from other types.

[@oafkad]

I really need to work on my presentation skills. These videos are always so enjoyable.

[@standupmaths]

It is all about practice. The more experience you have talking about mathematics, the better you get.

[@2003z440]

Wonderfully done with a great sarcastic sense of humor!

[@NoriMori1992]

6:44 - It took me several minutes of turning this sentence around in my head and playing with that simulator before I understood what you meant. Partly because I didn't know that you meant "the same distance from another point _as from_ a line"; and partly because I didn't know which line and which point you meant. Then suddenly, it finally clicked. XD So basically, you can make a parabola by selecting a point, drawing two lines perpendicular to each other (one fixed and one not), drawing a line from the first point to the point where the two lines meet, drawing the perpendicular bisector to _that_ line, marking the point where it meets one of your lines, then move the unfixed line one position over, and lather, rinse, repeat?! That's so cool!

[@Repsack2]

after a long work day, this was very relaxing and wonderful

[@TheCarenne17]

Failed my junior high math because I never understood a thing. Now I'm watching your video, it suddenly all makes sense

[@mikikaboom9084]

The proof's the best. So beautiful!

[@gawayne1374]

I just love this channel

[@CelloSeanMuller]

I have been subscribed for so long. Keep up the great content!

[@WJS774]

You say 'accidentally' the building was an approximation of a paraboloid, but I've heard that the architect had done the exact same thing with a building in Brazil previously, and it caused the same problem. It makes me wonder if it wasn't deliberate and the architect got a sick thrill out of it.

[@pizicek]

Another truly splendid video, as is the most of yours :) Great ending!

[@otakuribo]

Because of you and Numberphile, I am now watching videos on KZbin about my most hated subject in school. For FUN. And I'm LEARNING.

[@evilcam]

You were right once again Matt. I was indeed already subscribed. Is there anything you don't know? I remember the Sixty Symbols episode where Merrifield talks about that building and that very statue on the Nottingham campus. Seeing this proof actually helped me understand that video better. I should go watch it again to see if it really does make more sense now.

[@androidlogin3065]

There was a much easied way to visuali show it: A little smoke (to see ligth beams) and an array of led pointers that emit ligth like lasers in parallel pointing to the paraboloid. It is very visual and easy to do. Also it is very pleasant to show what happens when one ligth beam goes from parallel to a little non parallel, and if done with all causing a circle in the air instead of a focus point. Also can combine different colors on ligth beams.

[@giin97]

Just like the death ray of Vegas. Curved hotel focuses sunlight on its pool during the day. Was a little controversy over bad sunburns etc

[@whoeveriam0iam14222]

love your enthusiasm about maths

[@wazzup105]

Oh man those angular formulas.. I remember not studying that for my exam and having to recreate the formula and proofing (to myself at least) that it was correct during the exam.. so much fun :-)