how to easily write the epsilon-delta proofs for limits

แชร์
ฝัง
  • เผยแพร่เมื่อ 4 ก.พ. 2025

ความคิดเห็น • 437

  • @blackpenredpen
    @blackpenredpen  2 ปีที่แล้ว +11

    The ultimate introduction to the εδ definition th-cam.com/video/DdtEQk_DHQs/w-d-xo.html

  • @serenitymayfair623
    @serenitymayfair623 3 ปีที่แล้ว +354

    This taught me delta epsilon proofs better in 15 minutes than anyone else ever could in 10 hours of lectures

    • @richerram1
      @richerram1 3 ปีที่แล้ว +12

      Same here. Although I get the aversion to "easy step by step formulas" of some teachers I think some things are better taught with some sort of "fixed procedure" until you start getting the handle of it... great lesson.

    • @Redeemed_Daughter
      @Redeemed_Daughter 3 ปีที่แล้ว +2

      Tell me about it. I've been struggling for so long😅😅

    • @shivrajpatil1770
      @shivrajpatil1770 2 ปีที่แล้ว +1

      You mean 8 minutes and 27 seconds.

    • @kayceestudios6234
      @kayceestudios6234 2 ปีที่แล้ว +1

      @@Redeemed_Daughter yeah,I learnt the thing in just an 8 minutes video just imagine after wasting hours streaming useless videos that won't even explain what they are doing and why they are doing it

  • @osuh4947
    @osuh4947 3 ปีที่แล้ว +25

    Wow, this really is the single greatest video about Epsilon-Delta proofs.
    I have never seen some one explain this as detailed and well as this guy.

    • @schezum
      @schezum 3 ปีที่แล้ว +2

      I agree. This is the only video that enlightened me with this shit.

  • @Denis-vj2hz
    @Denis-vj2hz 4 ปีที่แล้ว +234

    I'm a simple man. If π≈3 and e≈3 then π≈e. Done ✅

    • @pyyrr
      @pyyrr 4 ปีที่แล้ว +84

      Hey look, it's an engineer!!

    • @El_Dr_Tacco
      @El_Dr_Tacco 4 ปีที่แล้ว +3

      Ha ha ha true but it'works, that's why you got an iphone in your hands.

    • @BiscuitZombies
      @BiscuitZombies 4 ปีที่แล้ว +1

      By pseudo-transitivity.

    • @akshatvats7992
      @akshatvats7992 3 ปีที่แล้ว

      If it's close enough, it's good enough

    • @chill4r585
      @chill4r585 8 หลายเดือนก่อน

      does anyone know why in the beginning we have to say "Given epsilon > 0" but not "delta > 0".
      Why cant we just "0 < |f(x)-L| < epsilon" just like delta?

  • @divishthamalik309
    @divishthamalik309 4 ปีที่แล้ว +22

    I have followed you through my high school and now I am still relying on your videos in my first year of engineering you have amazing content keep up the good work.Thanks a lot Sir.

  • @martinpena7949
    @martinpena7949 4 ปีที่แล้ว +270

    *In the one hour exam*
    "Oh I'm not sure about this limit, let me prove it"

  • @SergeantTeabag
    @SergeantTeabag 3 ปีที่แล้ว +9

    Extremely concise, thoughtful, and thorough explanation of how to use the epsilon-delta definition effectively and smoothly. This was so much more help than the book I'm reading through for Calculus. Thank you so much! This is a life-saver for college-level Calculus.

  • @AdelaCervantes-r4c
    @AdelaCervantes-r4c ปีที่แล้ว +2

    this might be the most useful video i've ever seen. somehow managed to gaslight me into thinking it was easy and simple and then it really became easy and simple thank you you are a magician

  • @tzonic8655
    @tzonic8655 4 ปีที่แล้ว +68

    I really had a hard time with epsilon-delta in my first semester in engineering but it turns out it's just matter of practice(for linear and 2nd degree polynomials 😅). It would be great if BPRP could show us geometrically the epsilon Delta

  • @kennethgibson288
    @kennethgibson288 4 ปีที่แล้ว +57

    This brings back so many memories!

  • @blackpenredpen
    @blackpenredpen  2 ปีที่แล้ว +12

    more examples:
    linear, square root, and quadratic 👉 th-cam.com/video/yC8Y50H6kw8/w-d-xo.html
    1/x and x^3 👉 th-cam.com/video/7VSG9G6EXrU/w-d-xo.html

    • @dunemeister5718
      @dunemeister5718 2 ปีที่แล้ว

      where did you get your shirt from????

    • @mikevaldez7684
      @mikevaldez7684 ปีที่แล้ว +1

      Shouldn't delta be smaller than epsilon? Such as Delta = e/3 ?

    • @m.ehsaan.
      @m.ehsaan. 23 วันที่ผ่านมา

      @@mikevaldez7684 yeah it is smaller than epsilon in this case, but that really doesn't make any difference and is unrelated to the proof.

  • @mohamedibrahim1023
    @mohamedibrahim1023 4 ปีที่แล้ว +29

    Best professor of all time♥️🔝

  • @dansantner
    @dansantner ปีที่แล้ว +1

    This is the best explanation I've ever seen. Every other Real Analysis lecture makes this way too difficult and confusing.

  • @Rachel-tu8pq
    @Rachel-tu8pq 2 ปีที่แล้ว +3

    exactly what I needed to help me in calc. love the way you can explain this dreaded topic so simply and have it be so effective!

  • @harisl5994
    @harisl5994 2 ปีที่แล้ว +1

    This man just explained the hardest topic in limits in just 15 Mins. Hats Off!!

  • @flyingcola7616
    @flyingcola7616 4 ปีที่แล้ว +32

    I've never seen a simpler walkthrough for this! Thank you so much! Calc AB final is coming up in a couple of days

    • @mikevaldez7684
      @mikevaldez7684 ปีที่แล้ว +1

      Hopefully you failed 🤣🙋🙏

    • @Ibrahim-tt3fx
      @Ibrahim-tt3fx 2 หลายเดือนก่อน

      yeah they arent on there lol

  • @imsonecka
    @imsonecka 2 ปีที่แล้ว

    i was reading a calculus book and i didn't understand a thing about this part but you made everything clear in 8 minutes! thank you so much!!!

  • @ikersanchez8222
    @ikersanchez8222 3 ปีที่แล้ว +3

    I wish I had found this video during my first college year. It is so well explained!

  • @BhaveeRathod
    @BhaveeRathod ปีที่แล้ว +1

    this dude's actually the best i can't even put it into words how grateful i am for him and his wonderful content!!

  • @smackdashitoutchu7755
    @smackdashitoutchu7755 3 ปีที่แล้ว

    Wouldnt have been ever able to grasp this concept otherwise without this video. Thanks.

  • @einsteingonzalez4336
    @einsteingonzalez4336 4 ปีที่แล้ว +176

    "GPA saver"...
    More like career saver. It's necessary.

    • @blackpenredpen
      @blackpenredpen  4 ปีที่แล้ว +18

      Definitely!

    • @benextinction__144
      @benextinction__144 4 ปีที่แล้ว +7

      I thought you were me for a second and I was going loopy watching videos I'd already seen. Never seen anyone else with a map of CMB radiation as a profile pic. :)

  • @shawnpcyril4200
    @shawnpcyril4200 3 ปีที่แล้ว +3

    Every Math professor should be simple, clear and paced as you are. Thanks a ton !

  • @UnevenerGgc2
    @UnevenerGgc2 4 ปีที่แล้ว +1

    I’m not taking calc(not old enough yet to take it lol) but it was always difficult for me to wrap my head around quadratic epsilon delta proofs, it feels like this opened my 3rd eye

  • @mathosophy3655
    @mathosophy3655 3 ปีที่แล้ว +2

    For the last problem, we could instead choose δ to be (sqrt(49 + 4ε)-7)/2, and it would be a less strict condition as min{1,ε/8} ≤ (sqrt(49 + 4ε)-7)/2 for all ε. If, say hypothetically, we had to pay according to how small we chose δ to be, then we wouldn't want to choose it any smaller than we actually need to. In that case, the more complicated expression would cost the least. In any case, it was a great video, as always!

  • @Bayesic
    @Bayesic 4 ปีที่แล้ว +12

    Where was this kind of content when I was in calc 1? Amazing video man!

    • @aliaziz1145
      @aliaziz1145 3 ปีที่แล้ว

      This isn’t in calc 1 b/c u don’t focus on proofs in that course. This content comes up in advanced courses

    • @Bayesic
      @Bayesic 3 ปีที่แล้ว +3

      @@aliaziz1145 we definitely had a couple sections in my calc 1 class that were dedicated to delta epsilon proofs. Technically optional but not as far as my teacher was concerned haha

    • @aliaziz1145
      @aliaziz1145 3 ปีที่แล้ว +1

      @@Bayesic this definition of a limit is so much more satisfying than the lower level sanitized definition from freshman year college 😂

  • @MichaelDuder
    @MichaelDuder 3 ปีที่แล้ว +1

    Thank you so much for this... I am trying to get a headstart on calc out of Stewarts Calculus and they really don't do a very good job of explaining in the text so you just got me dug out of a ditch trying to understand what to do with exponents.

  • @_AmitabhShukla
    @_AmitabhShukla 3 ปีที่แล้ว

    DAMN! you explained it to me in just 15 minutes and I was struggling with it for last 2 hours . ......Thanks , man.

  • @chrisxd146
    @chrisxd146 4 ปีที่แล้ว +6

    I almost wish my university would've had more time to focus on the delta-epsilon proof. We never went over the notation used for the limit of the quadratic so thankfully I learned about it before moving on from being an undergrad.

  • @frostinfy169
    @frostinfy169 4 ปีที่แล้ว +3

    I've never been thought this method. I'll try to practice with it!

  • @tharinduprabhath3377
    @tharinduprabhath3377 3 ปีที่แล้ว

    Dude I was so fucked up by delta and Epsilon... You just solved it under 15 min.. Cool man.. You are a really good teacher.. Good Luck ❤️❤️❤️

  • @iwonthide
    @iwonthide 4 ปีที่แล้ว +3

    was waiting for this video thanks man ❤️

  • @ellielinyan1521
    @ellielinyan1521 3 ปีที่แล้ว +3

    watching this 2 days before my calculus paper and suddenly it all makes sense...LMAOOOO

  • @BiscuitZombies
    @BiscuitZombies 4 ปีที่แล้ว +1

    Thanks. I'm not in university yet, but I do like calculus and I think this is important.

  • @amyholmes8373
    @amyholmes8373 3 ปีที่แล้ว

    Better explanation than the lecturers at uni, tysm!

  • @w7lves
    @w7lves 3 ปีที่แล้ว

    this is kind of on me for not attending class after convo, but this man probably just saved me

  • @jaloliddinzukhriddinov5820
    @jaloliddinzukhriddinov5820 3 ปีที่แล้ว +1

    Thanks so much, you helped me to understand easily and fully about limits with epsilon, delta, thanks so much for your videos

  • @isaklyon7660
    @isaklyon7660 3 ปีที่แล้ว

    thank you bro you explained better than my lecture did in 2hrs

  • @shivrajpatil1770
    @shivrajpatil1770 2 ปีที่แล้ว

    The last sentence of "We Are Done." is too satisfying!!!

  • @TheKiller-me3uy
    @TheKiller-me3uy 11 หลายเดือนก่อน +1

    كبيييير واصلي دوووود

  • @adityakulkarni9230
    @adityakulkarni9230 4 ปีที่แล้ว +9

    Learned something new. This was a bit different from other vids as I could try the problems along with you. Really a great experience.
    Please do keep having more such alongside trial videos.
    BPRP Yay!

  • @2manynathans
    @2manynathans 2 ปีที่แล้ว +1

    excellent video! It was the one that finally made it make sense!!!!!!!

  • @Chris-ng9zi
    @Chris-ng9zi 3 ปีที่แล้ว +5

    For the second example where you said (@(8:27) root (2x+6) is always positive and thus {(2|x-5|) / (root(2x+6) + 4)} < (2|x-5|) / 4. Instead, could you have said the entire denominator (root(2x+6) + 4) is also positive and thus { (2|x-5|) / (root(2x+6) + 4) } < (2|x-5|). The result is that delta is equal to Epsilon/2 vs 2.epsilon. Is "Epsilon/2" an acceptable answer?

  • @ludwigfredriksson3786
    @ludwigfredriksson3786 4 ปีที่แล้ว

    Thanks, you explained it much better than my professor. It clicked!!

  • @kr4301
    @kr4301 4 ปีที่แล้ว

    I wish I had these videos back in times i was taking calculus I class. However I succeed my Calculus I part 2 exam (mostly based on series and series of functions) thanks to your videos

  • @muhammadmuaaz3704
    @muhammadmuaaz3704 2 ปีที่แล้ว

    Bro you are nothing less than a life saver man thanks a lot bruh this video is amazing. .

  • @hb1318
    @hb1318 ปีที่แล้ว

    You're a lifesaver. Thank you!

  • @foudilbenouci482
    @foudilbenouci482 2 ปีที่แล้ว +1

    Thank you very much you explaination is very efficient

  • @laizquierdomx
    @laizquierdomx 3 หลายเดือนก่อน

    thank you sir you saved my exam !!

  • @ayberkkarakas6898
    @ayberkkarakas6898 3 ปีที่แล้ว +1

    You're awesome mate!

  • @WritersDigest-b8f
    @WritersDigest-b8f ปีที่แล้ว +1

    Enjoyed it, explained with clarity, thank u, I will look for similar examples on YT from you to be able to solve all problem of this nature.

    • @blackpenredpen
      @blackpenredpen  ปีที่แล้ว

      Glad it was helpful! This is the video
      24 rigorous limit proofs (ultimate calculus tutorial)
      th-cam.com/video/AfrnYS5S8VE/w-d-xo.html

  • @dognip
    @dognip 4 ปีที่แล้ว

    I've just started calculus. It's nice

  • @strixytom
    @strixytom 4 หลายเดือนก่อน +1

    That was a really nice video. Thanks!

  • @epsa9324
    @epsa9324 3 ปีที่แล้ว

    taught better than our college professor..... do uploa more videos.....

  • @AJ69238
    @AJ69238 3 ปีที่แล้ว

    Excellent explanation! You're a life saver, man!

  • @MrDZ-xc9ip
    @MrDZ-xc9ip 2 ปีที่แล้ว

    Thanks teacher
    You save my life

  • @thiwankapathirana9532
    @thiwankapathirana9532 2 ปีที่แล้ว +1

    Thank you so much for your help sir.

  • @cellothere5723
    @cellothere5723 ปีที่แล้ว +1

    This is an amazing video, thank you so much!!

  • @phyokhant6472
    @phyokhant6472 4 หลายเดือนก่อน

    thanks god I found you before my next week exam.

  • @sajinilakshika5000
    @sajinilakshika5000 2 ปีที่แล้ว

    I got an A for real analysis (continuous/discontinuous functions ) just bcz of this 8 minutes video.. tnx blackpenredpen ❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤

  • @jimmorrison6177
    @jimmorrison6177 4 ปีที่แล้ว +1

    In the second problem you need d=min{8,2e} because in the current state, for e=5 we get d=10 but then x can be -4 (0

    • @angelmendez-rivera351
      @angelmendez-rivera351 4 ปีที่แล้ว

      No, because x = -4 is not in the domain of the function in question anyway.

  • @taurus7868
    @taurus7868 7 หลายเดือนก่อน

    It always amazes me how smooth and fast you can shift your pen colors..

  • @Redeemed_Daughter
    @Redeemed_Daughter 3 ปีที่แล้ว

    You are the best man🥺🥺 thankyou

  • @spider-uh5ws
    @spider-uh5ws 4 ปีที่แล้ว +5

    bro I am 14 and this is so nice and understandable, honestly you are the best teacher ever.

  • @valsnemakonde6936
    @valsnemakonde6936 4 ปีที่แล้ว

    Thank you so much, i should have known this channel before

  • @alifetimeoflearning
    @alifetimeoflearning ปีที่แล้ว

    It is so important to keep sharp with these proofs. In today’s world of “dumbing down” we are graduating students who, more or less are not able to think outside of the box. #alifetimeoflearning.

  • @natnaelh.baraki2869
    @natnaelh.baraki2869 3 ปีที่แล้ว +2

    What about for the cases when X approaches to infinity?🙏🏽

  • @technicalbrains7675
    @technicalbrains7675 4 ปีที่แล้ว +3

    That Pokeball looks awesome 😁

  • @approachinglimits
    @approachinglimits 2 ปีที่แล้ว

    Thank you for this video! I could not figure out how to do the quadratics of these for the life of me. The answer key in the back of the book has the answer but no sufficient explanation. And the only other example I could find on TH-cam was of a quadratic the factored to a perfect square which comes out much nicer in these circumstances.

  • @Mrsidd328
    @Mrsidd328 4 ปีที่แล้ว +37

    I swear I heard him say "Idiot" at 2:28 (I know he says "in the end" but it confused me for a minute)

    • @przemezio
      @przemezio 4 ปีที่แล้ว +3

      It sounds like "in D yet" :)

    • @valsnemakonde6936
      @valsnemakonde6936 4 ปีที่แล้ว

      live lol

    • @navaerick86
      @navaerick86 4 ปีที่แล้ว

      I felt like he was speaking directly to me.

    • @j.6230
      @j.6230 3 ปีที่แล้ว

      @@navaerick86 To me as well, and he's right

  • @alexandremargar123
    @alexandremargar123 3 ปีที่แล้ว

    Thx thx really thx it took me several years to understand that damnned e-d stuff until I see your video.

  • @zayedsalim5333
    @zayedsalim5333 2 ปีที่แล้ว +1

    At 6:26, why we can't say that it's less than 2*|x-5| (in stead of 2*|x-5| over 4)? so delta = epsilon/2...

  • @Engineering_conceptsUOM
    @Engineering_conceptsUOM 3 ปีที่แล้ว +1

    Excellent … thank you so much sir…

  • @chileshesikazwe8500
    @chileshesikazwe8500 3 ปีที่แล้ว

    thank you from Zambia

  • @ShermukhammadKarimov
    @ShermukhammadKarimov 9 หลายเดือนก่อน

    thanks for clear explanation

  • @jeremypolancolara2154
    @jeremypolancolara2154 2 ปีที่แล้ว

    Nice explanation, very clear

  • @joseph-ianex
    @joseph-ianex 9 หลายเดือนก่อน

    Great video! I'm a bit confused when I was supposed to learn this though because I'm taking Calc 2 now and was never taught this in Calc 1 or 2 so I guess the teachers assumed it wasn't important or just didn't have time

  • @AyushsinghDhanola
    @AyushsinghDhanola วันที่ผ่านมา

    Very great explanation

  • @anikbhowmick1044
    @anikbhowmick1044 4 ปีที่แล้ว

    Please make same type of video on two variable limits also . I am going through limits of two variables in my college but mostly sticking on proving the limit through epsilon delta definition

  • @ahadkhan7290
    @ahadkhan7290 3 ปีที่แล้ว

    great explanation, made a complicated topic seem easy and simple!

  • @ninjapirate123
    @ninjapirate123 9 หลายเดือนก่อน

    This dude is a legend

  • @zayk9532
    @zayk9532 3 ปีที่แล้ว

    I actually understood it. My teacher is great but I just need a little more time to learn the concept.

  • @medhanitgetachew1706
    @medhanitgetachew1706 4 ปีที่แล้ว

    Tnxs you are a savior it was fun 👍👍

  • @lmc_x_hep9356
    @lmc_x_hep9356 2 ปีที่แล้ว

    Wow bro, u are so brilliant, I like u bro, u help me so much to understand

  • @rishikagudlavalleti5241
    @rishikagudlavalleti5241 4 ปีที่แล้ว +1

    This was so helpful thank you 😁😁🙏🙏

  • @younesyounes3503
    @younesyounes3503 3 ปีที่แล้ว

    Thanks, I understand this well

  • @qin2500
    @qin2500 3 ปีที่แล้ว

    AY YO! Bro, my midterm is tomorrow, you just saved my ass.

  • @Nikolaij02
    @Nikolaij02 3 ปีที่แล้ว

    thank you this is exactly what i needed

  • @hqs9585
    @hqs9585 3 ปีที่แล้ว

    I do like your lectures but I have a few comments in this delta epsilon subject. Suppose(?) that is a big step to come out with possible delta. One should first work with the f(x) and find factors, then from there you start your delta value. The value of epsilon you get by just dividing by a factor to make it ! is also arbitrary. Just compare the |f(x) - limit value| and from there you automatically get that fraction relating delta and epsilon. Thanks

  • @umat4892
    @umat4892 3 ปีที่แล้ว +1

    Could you please solve this?
    Let lim n approaches to Infinity
    n(cube root of(n^3+6n^2+3n+2)+
    square rootof (n^2-4n+2)-2n) = p/q where p and q are coprimes then the value of p+q is equal to ?
    Please make a video on this!

  • @ElemenTalParkour
    @ElemenTalParkour 3 ปีที่แล้ว +1

    great explamation!!! do you have some examples with x going to infinity ?

  • @aidenhastings6341
    @aidenhastings6341 3 ปีที่แล้ว +4

    Thank you! Do you have explanations of delta epsilon proofs in other contexts than just a limit (such as limit of a sequence, uniform continuity, etc)?

    • @blackpenredpen
      @blackpenredpen  3 ปีที่แล้ว +2

      th-cam.com/video/2xmKUBgWk78/w-d-xo.html

  • @mikoajmackowiak6993
    @mikoajmackowiak6993 4 ปีที่แล้ว +1

    Even tho, I don't need this at school now, cool video.

  • @raghadsan603
    @raghadsan603 3 ปีที่แล้ว

    that was so clear thanks

  • @paulnelson112
    @paulnelson112 4 ปีที่แล้ว

    Awesome video, u know real numbers so good 👌👌

  • @firenzetanke2272
    @firenzetanke2272 3 ปีที่แล้ว

    This is so much more understandable than how my professor explained it to me

  • @therandomvidguy5141
    @therandomvidguy5141 4 ปีที่แล้ว

    can you please love this for no reason

  • @رشاداليامي
    @رشاداليامي 4 ปีที่แล้ว

    I live them these problems about analysis of real
    Thank u so much agreat teacher ... u were studying in university

    • @رشاداليامي
      @رشاداليامي 4 ปีที่แล้ว

      Im sorry i means u remember were studying in university

  • @muhammadfazlanjohan-chalce161
    @muhammadfazlanjohan-chalce161 3 ปีที่แล้ว

    Alhamdulillah , Akhirnya ada subtitle indonesia , sama ini hanya memahami dari angka dan tulisan aja :)

  • @MrCrazydooker
    @MrCrazydooker 3 ปีที่แล้ว +2

    7:30 Since we can remove the square root part of the denominator which makes the resulting fraction is bigger, couldn't we just remove the positive denominator all together? That would result in 2abs(x - 5) < ε which gives us δ = ε/2. You ended up with δ = 2ε. Are both okay or am I missing something here?

    • @adirbarak5256
      @adirbarak5256 3 ปีที่แล้ว

      I think that's true but in the context of a "step by step tutorial" it might be for the best that he doesn't go the most direct efficient path. Anyway thank you for your comment, I hadn't notice it.

    • @McBlueskai
      @McBlueskai 3 ปีที่แล้ว

      Hey im also interested in that, why not remove the whole denominator?

    • @thisis_shashwat
      @thisis_shashwat 2 ปีที่แล้ว

      Both okay, to check you can give some values to epsilon or delta,
      Eg you can take delta as 1 & epsilon as 2.
      You'll see that they satisfy both inequalities

  • @mr.jennycano1701
    @mr.jennycano1701 3 ปีที่แล้ว

    very nice presentation. Thanks man!