U-substitution with definite integral

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  • čas přidán 27. 12. 2012
  • Example of using u-substitution to evaluate a definite integral
    More free lessons at: www.khanacademy.org/video?v=7h...

Komentáře • 96

  • @warwick802
    @warwick802 Před rokem +11

    For calculus 2 you basically choose to either plug back "u" and leave the bounds alone or change the bounds and leave it as u.

  • @GatorsCloset
    @GatorsCloset Před 11 lety +3

    This video is more complicated than it needs to be. When you substitute the "1/2x" into the integral you'll have "x/2x" the x will disappear and you'll be left with "1/2" and since it is a multiplier you just bring the one half outside of the integral. This is a lot more simple than multiplying by two and one half to keep the integral the same in order to have a "2x/2x".

  • @gracepackard6838
    @gracepackard6838 Před 7 lety +5

    Sal, you are the light of my life.

  • @ghgoodreau-old
    @ghgoodreau-old Před 8 lety +4

    You have no idea how much you've helped me out this semester. I'll do my best to pay it forward!

  • @HotPepperLala
    @HotPepperLala Před 11 lety +4

    Sal sounds so organized and prepared now. But for some reason I like the old Sal videos lol

  • @allieyi
    @allieyi Před 6 lety +5

    Thanks so much! I have test this morning, and I needed this!

  • @melikyuksel4527
    @melikyuksel4527 Před 9 lety +17

    I love you Sal, you did in 5 minutes what my textbook did in 30.

  • @Heirophanteye
    @Heirophanteye Před 11 lety +1

    Sorry, I have a Masters in both Business Admin and Accounting. I took AP Calculus AB and BC in High School but didn't have to in college. I am always looking to improve myself so I am trying to learn new things; such as refreshment on calculus and physics topics.

  • @humiraarroyo
    @humiraarroyo Před 6 lety +4

    thank you! so so helpful and straightforward!

  • @muffemod
    @muffemod Před 6 lety +11

    Warning: In order to use substitution, the intergrand must contain the derivative of the inside function, to within a constant factor.

    • @pram5532
      @pram5532 Před 2 lety +3

      tf is an intergrand

    • @JasonVaysberg
      @JasonVaysberg Před 2 lety +5

      @@pram5532 the function that is going to be integrated. xsin(x^2) is the integrand in this case.

    • @NewWesternFront
      @NewWesternFront Před rokem +2

      @@pram5532 it's a form of ligma

    • @jonathanalonso6492
      @jonathanalonso6492 Před rokem +1

      @@pram5532 An integrand is the result from basically converting an integral back into a higher-order function. An integral is the same as getting the derivative of whatever higher-order function you started off with. For example: an integral, like 2x, is what you get after differentiating x^2.
      They are opposites of each other.

  • @Thedreamshaperabc
    @Thedreamshaperabc Před 11 lety +1

    Well often this would be only a very small part of a larger application, not all things can by it self be directly applied. I truly get how we want things to have a direct application, but sometimes one simply needs to take a leap of faith and try to learn the theory and realize than unless one wants to go into plumbing and construction, some times things will get abstract :)

  • @joelplascencia3568
    @joelplascencia3568 Před 8 lety +48

    You see, I understand how to do it now, but I still don't get the purpose.

    • @GrimmjowJaegerjaquez
      @GrimmjowJaegerjaquez Před 6 lety +25

      Joel Plascencia it's been two years, do you get the purpose yet?

    • @thebanish3r355
      @thebanish3r355 Před 4 lety +1

      3?

    • @jamesrich3161
      @jamesrich3161 Před 4 lety +3

      3 years later and your question still stands buddy

    • @mohammedhoque7671
      @mohammedhoque7671 Před 4 lety +3

      4 years still no purpose??

    • @joelplascencia3568
      @joelplascencia3568 Před 4 lety +13

      @@mohammedhoque7671 I posted this during my senior year of high school. I'm now a fourth year of college, and I learned the purpose about 2 years ago

  • @sarahholland5980
    @sarahholland5980 Před 6 lety

    Completely forgot how to do u-substitution and my exam is in two weeks. Thanks Sal!

  • @Heirophanteye
    @Heirophanteye Před 11 lety +1

    I suppose everyone is entitled to their opinion; which is why I expressed mine. I like that integral calculus has uses. I was simply suggesting that before or perhaps during the explanation of the technique being taught that use of technique in a real world example would be helpful. If I hand you a tool and fail to teach you what it can be used for, I am relying upon you to figure out how to use it. Sure, eventually I may figure it out but it's faster to teach me up front what it is used for.

  • @agent-sz2qj
    @agent-sz2qj Před 7 lety +2

    substitution was my nightmare, but not anymore thanks to you

  • @MrMarkgyuro
    @MrMarkgyuro Před 4 lety

    thank you khan! very good explanation!!

  • @danhassler6585
    @danhassler6585 Před 3 lety +1

    Great! makes it easy to understand.

  • @boihi1496
    @boihi1496 Před 5 lety +1

    This helps so much ty for review

  • @user-ub2dp7fp2d
    @user-ub2dp7fp2d Před 7 lety +1

    do we need to +C again in behind of result, sal??? thanks.. you enlighten the enlightenment

    • @zestyorangez
      @zestyorangez Před 7 lety +3

      no because the integral is definite

  • @NightSwipe17
    @NightSwipe17 Před 10 lety

    Thank you so much, I finally understand this.

  • @pa800korg92
    @pa800korg92 Před 10 lety +1

    AWESOME TEACHER!!!!!

  • @zixan
    @zixan Před 11 lety

    what a good refresher after five years of no math class

  • @zldms93
    @zldms93 Před 11 lety

    정리진짜잘하당ㅎㅎ

  • @emmanuelphiri2086
    @emmanuelphiri2086 Před 7 lety

    thanks so much SIR you saved my time

  • @DRJACOBB
    @DRJACOBB Před 11 lety

    I was an award winning teacher--in the fourth largest district in the United States, I harnessed the power of technology to take my students to places they have never been! I provided implementation ideas to my school and the children really benefitted. More power to you! By the way, "Giving Our Students the World" is my motto and it is now the motto for ~ 400,000 students. So, yes, I AM a caring teacher--that's my philosophy.

  • @likesomehero
    @likesomehero Před 11 lety

    You are the reason why education in America needs reform

  • @inglesyeses
    @inglesyeses Před 11 lety +1

    hi. i have a feeling you should write the 'd' properly, otherwise people could get confused later with partial differential equations where the d's are written more curly like in your vid... just a thought.

  • @EytanWallace
    @EytanWallace Před 11 lety

    Yes. As long as you don't accidentally take the antiderivative in terms of U with the X bounds.

  • @keotshepilemandona9882

    THANKS KHAN ......

  • @taylorkamann21
    @taylorkamann21 Před 7 lety

    👋🏽 Sal you're the best.

  • @MiladD25
    @MiladD25 Před 10 lety

    At which school level did you guys first did this? high school or college?

  • @joose9748
    @joose9748 Před 6 lety +3

    try showing an example of substitution when you cant use the u' straight on ...these are type "Oh look at that how lucky am I there is u' sitting right next to my u"...

  • @go2grave01
    @go2grave01 Před 11 lety

    We use functions for all kinds of things(physics,computer science,astronomy).

  • @danielpersaud2008
    @danielpersaud2008 Před 10 lety

    do u always always always take the new limits?

  • @odefeoberabor7597
    @odefeoberabor7597 Před 9 lety

    Bravo ! Thanks

  • @SerdnaZe
    @SerdnaZe Před 9 lety

    What happened to u=x^2 at the end?

  • @EvilMastermind
    @EvilMastermind Před 7 lety +5

    I freaking HATE integrals. I am litteraly never going to use them in my entire life and I am forced to learn them. Plus to make things worse, every person I watch who is calculating integrals does it completely different somehow. Jus out of the blue every time...

    • @muffemod
      @muffemod Před 6 lety +4

      You will be faced with problems in life. You will be forced to solve them. If you can apply logic and reasoning to solve problems in mathematics, you can transfer those skills into other areas of life.

    • @evanmastermind
      @evanmastermind Před 5 lety

      @@muffemod Wrong.

  • @Knexfoof
    @Knexfoof Před 11 lety

    Saviour Sal Strikes Again! Thanks Sal :)

  • @dr.willisofficial8041
    @dr.willisofficial8041 Před 29 dny

    Thank you so much!

  • @ricois3
    @ricois3 Před 11 lety

    Sign of you!

  • @kane3743
    @kane3743 Před 7 lety

    thank you

  • @ab.bull117
    @ab.bull117 Před 2 lety

    Thakn you

  • @EytanWallace
    @EytanWallace Před 11 lety

    Can someone please briefly explain why we need to multiply by 2 and .5 in the beginning?

  • @domestic_god
    @domestic_god Před 11 lety

    Is this A-Level or Degree level mathematics?

  • @jamesbra4410
    @jamesbra4410 Před 6 lety

    Nobody learns when you pick the easiest example

  • @Heirophanteye
    @Heirophanteye Před 11 lety

    Wow. I really need to go back to college. Two master's degrees and I still don't understand the application of this math. What would I even use it for? These videos could be significantly enhanced by starting with a real-world use so that I can start integrating the knowledge by seeing it in context. Then I could understand how the components fit together. Math for math's sake is dry; even for someone who loves learning new things.

    • @eleftheriosgkioulekas1001
      @eleftheriosgkioulekas1001 Před rokem

      Mathematics IS a real world. You use substitution to do integrals. E.g. it can reduce a wide range of trigonometric integrals to rational integrals. Among other things.

  • @Avdbz
    @Avdbz Před 11 lety

    obviously you haven't paid much attention during class, integrals are used to solve,max-mini equations, in fysics, for calculating the area under a curve, it s used extensively in economics alongside with derivatives.... my man if only you would take the time to have a greater look in to every practical thing around us, you would quickly realize that 90% is built upon math... so not math for math s sake is not dry. it s all around us...

  • @sveta89
    @sveta89 Před 11 lety

    this is great but i could have used it five months ago ... when i needed it badly

  • @DRJACOBB
    @DRJACOBB Před 11 lety

    By the way, I remember calculus, but the thing that brought me here was Nightline. The One World School book sounds like it is perfectly aligned with my philosophy--a must read for me. Great job, my friend--and I, too, have an M.B.A. but taught children out of love.

  • @Schiltzy_ISU
    @Schiltzy_ISU Před 5 lety +1

    are you a god?

  • @alexdrudigmail
    @alexdrudigmail Před 11 lety

    Would you mind stating the area of your academic studies? I mean no disrespect, I'm just appalled to realize that teachers at post-graduate level can avoid explaining the huge real world impact of basically any branch of calculus.

  • @badboyesed
    @badboyesed Před 11 lety

    why there is no professor like you in my college ... my wold have bean easier :$

  • @FajorMuckup
    @FajorMuckup Před 11 lety

    I mean you just see its -cos(x^2) without substitution after a while

  • @heavymetaldeath4life
    @heavymetaldeath4life Před 11 lety

    "Math for math's sake is dry; even for someone who loves learning new things."
    Pure mathematicians like G. H. Hardy would strongly disagree.
    Besides, integral calculus is used in areas like electromagnetism, and by extension electrical engineering.

  • @hilalbasibuyuk3459
    @hilalbasibuyuk3459 Před rokem

    görselliği bile mükemmel

  • @changjin1229
    @changjin1229 Před 11 lety

    쉽다

  • @rzxwm10
    @rzxwm10 Před 11 lety

    calculus

  • @eaflores93
    @eaflores93 Před 11 lety

    9th

  • @1234airows
    @1234airows Před 11 lety

    algebra

  • @iComicE
    @iComicE Před 11 lety

    2nd

  • @w2010rcdas
    @w2010rcdas Před 11 lety

    3rd

  • @ngotuan0881
    @ngotuan0881 Před 11 lety

    12th grade level mathematics./.

  • @stopdropandroll
    @stopdropandroll Před 11 lety

    most likely trolling lol

  • @thoriso1000
    @thoriso1000 Před 10 lety +1

    Still confused :'(

    • @OSMADO
      @OSMADO Před 10 lety +3

      you have to study antiderrivatives to get this... it's pretty simple once you practice it and get it through your head

  • @tuber324
    @tuber324 Před 11 lety

    Please tell me you're kidding. -.-

  • @Shihai0Tensei
    @Shihai0Tensei Před 11 lety

    a-level

  • @wntrsldr5077
    @wntrsldr5077 Před 6 lety

    This subject = kms

  • @tigerclaw3211
    @tigerclaw3211 Před 11 lety

    1st

  • @badboyesed
    @badboyesed Před 11 lety

    my life* wold have bean easier :$

  • @elitesniper3211
    @elitesniper3211 Před 11 lety

    This is BORING