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blackpenredpen
United States
Приєднався 29 гру 2012
This channel is about math for fun! Most of the topics will be calculus-based. Sometimes we will also investigate some weird equations and complex numbers! Feel free to subscribe if you also like math!
If you are looking for calculus tutorials for your #precalculus, college #calculus1, college #calculus2, #APcalculusAB, or #APcalculusBC, then please visit my "just calculus" channel: bit.ly/just_calc
If you are looking for calculus tutorials for your #precalculus, college #calculus1, college #calculus2, #APcalculusAB, or #APcalculusBC, then please visit my "just calculus" channel: bit.ly/just_calc
Відео
Meet the 94-year-old calculus teacher! @ycmathematicsphysicsandche5659
Переглядів 19 тис.День тому
Thanks to the UA-cam algorithm, I discovered Mr. Feng, a 94-year-old calculus teacher, @ycmathematicsphysicsandche5659 . He said in his note that teaching makes him happy and makes his life meaningful, which I resonate with so much. I want to make a video to introduce him to you! Please consider subscribing to his channel and supporting what he does. Thank you. The solution to the derivative ch...
First time solving an A-Level maths exam! (90 minutes, uncut)
Переглядів 117 тис.21 день тому
I will be doing a British A-Level further maths paper on the spot for the first time! This paper contains mainly algebra and calculus. Topics include complex numbers, hyperbolic equations, exponential equations, trigonometric identities and equations, first-order linear differential equations, determinant and the inverse of a 3x3 matrix, and more! Was I able to solve all the questions within 90...
The notorious three-circle problem from the GCSE
Переглядів 71 тис.21 день тому
Get started with a 30-day free trial on Brilliant: 👉brilliant.org/blackpenredpen/ ( 20% off with this link!) Here's the last question from the 2022 GCSE maths paper that made the news. We have three circles as shown and each radius is 4 cm. We have to find the area of the shaded region in the middle. I made a horrible mistake last time when I said the area of a circular sector is r*theta. The c...
Solutions to the 2023 AP Calc AB FRQ
Переглядів 31 тис.Місяць тому
Get started with a 30-day free trial on Brilliant: 👉brilliant.org/blackpenredpen/ ( 20% off with this link!) We will go over ALL the free response questions from the 2023 AP Calculus AB test to help you prepare for the upcoming AP exam. Topics included defined integral, average value of a function on an interval, change in position vs total distance traveled, implicit differentiation, related r...
You see nonlinear equations, they see linear algebra! (Harvard-MIT math tournament)
Переглядів 129 тис.Місяць тому
Get started with a 30-day free trial on Brilliant: 👉brilliant.org/blackpenredpen/ ( 20% off with this link!) This system of nonlinear equations is from the general round of the 2023 Harvard-MIT math tournament. www.hmmt.org/www/archive/271 I will present the linear algebra method I learned from their official solution to solve this system because I thought it was fascinating. It's from Harvard ...
Which is the worst math debate: 0^0, sqrt(1), 0.999...=1, or 12/3(4)?
Переглядів 243 тис.2 місяці тому
These are the most debated math topics on the Internet but which one is the worst? (A) 0 to the 0th power=1 or undefined. No calculus limit here. (B) sqrt(1) = 1 or both -1?) (C) 0.999...=1 or not? (D) order of operations 12/3(4)=1 or 16 More than 28,000 viewers voted in my recent poll and now let's discuss what each debate is all about. 🛍 Shop my math t-shirt & hoodies: amzn.to/3qBeuw6 💪 Get m...
You wouldn’t expect this "quadratic" equation to have 6 solutions!
Переглядів 116 тис.2 місяці тому
Surprisingly, the "quadratic" equation x^2 5abs(x)-6=0 has a total of 6 solutions (2 real and 4 complex solutions) which I did not expect. I came up with this equation purely by accident and I think it is super cool. It will feature complex numbers! 🛍 Shop my math t-shirt & hoodies: amzn.to/3qBeuw6 💪 Get my math notes by becoming a patron: www.patreon.com/blackpenredpen #blackpenredpen #math #c...
Using a logarithm property to make this equation easier!
Переглядів 87 тис.2 місяці тому
Get started with a 30-day free trial on Brilliant: 👉brilliant.org/blackpenredpen/ ( 20% off with this link!) We will solve this power equation x^ln(4) x^ln(10)=x^ln(25). However, the process of solving this equation would require making one side equal to 0 but factoring every term by x^ln(4), and I don't think the expressions will look that nice. So instead, we can use the log property that a^l...
My first calculus 3 limit on YouTube
Переглядів 88 тис.3 місяці тому
Get started with a 30-day free trial on Brilliant: 👉brilliant.org/blackpenredpen/ ( 20% off with this link!) This is my first video on a multi-variable limit that you will see in your Calculus 3 class. We will evaluate the limit of y/x as (x,y) goes to (0,0) but how do we take care of this? We do get 0/0 indeterminate form but can we use L'Hopital's rule? 0:00 Limit of y/x as (x,y) goes to (0,0...
Believe in geometry, not squaring both sides!
Переглядів 254 тис.4 місяці тому
Get started with a 30-day free trial on Brilliant: 👉brilliant.org/blackpenredpen/ ( 20% off with this link!) We will solve the equation that has two square roots sqrt(16-x^2) sqrt(9-x^2)=5 with a cool geometric triangle trick. In the end, we will also see if ChatGPT can solve this equation by using geometry. Check out a similar video on the proof of the Pythagorean Theorem and its inverse: ua-c...
Solution of the transcendental equation a^x+bx+c=0
Переглядів 149 тис.5 місяців тому
Learn contest math on Brilliant: 👉brilliant.org/blackpenredpen/ (now with a 30-day free trial plus 20% off with this link!) Today we will find a general solution to the transcendental equation a^x bx c=0. Here's an example 2^x-3x-1=0 ua-cam.com/video/GJbzsmccFtw/v-deo.html Check out a detailed the Lambert W function introduction: ua-cam.com/video/Qb7JITsbyKs/v-deo.htmlsi=bKnZW_lqlDjiKQuf 0:00 s...
My failed attempts to the integral of sqrt(sin^2(x))
Переглядів 108 тис.5 місяців тому
I have been trying to integrate sqrt(sin^2(x)) and get the same answer as on WolframAlpha, which is -sqrt(sin^2(x))*cot(x) C, but I just can't. So let me show you what I have tried (including how to integrate sqrt(x^2) with integration by parts) and maybe some of you will have an idea! 🛍 Shop Ultimate calc 2 integral sweatshirt: www.amazon.com/dp/B0C9L798F2 💪 Support the channel and get feature...
if x+y=8, find the max of x^y
Переглядів 674 тис.5 місяців тому
If x y=8 for nonnegative x and y, then find the maximum value of x^y. This question seems like a typical calculus optimization problem, but to find the exact answer, we will need to use the Lambert W function. ua-cam.com/video/Qb7JITsbyKs/v-deo.htmlsi=lc0IZ6aTrvewRBIh Check out my 100 calculus 2 problems to help you with your calc 2 final: ua-cam.com/video/Kwyk_mteyNc/v-deo.htmlsi=Dj_3rv2qeen7S...
Calculus teacher vs L'Hopital's rule students
Переглядів 83 тис.5 місяців тому
If you are also a calculus teacher, then you know most students will just use L'Hospital's rule for every limit after they learn the rule. So let's investigate the limit as x goes to infinity of (the integral from 0 to x of sin(t)*e^cos(t))/x and see why we cannot use L'Hôpital's rule. This is a great challenging limit problem for your calculus students! #calculus #blackpenredpen #challenge Rel...
combining rational exponents, but using calculus,
Переглядів 95 тис.5 місяців тому
combining rational exponents, but using calculus,
easy derivative but it took me 32 minutes
Переглядів 176 тис.6 місяців тому
easy derivative but it took me 32 minutes
I couldn't solve x^x^x=2, so I solved x^x^(x+1)=2 instead
Переглядів 124 тис.6 місяців тому
I couldn't solve x^x^x=2, so I solved x^x^(x 1)=2 instead
all solutions to 2^x-3x-1=0 (transcendental equation)
Переглядів 140 тис.6 місяців тому
all solutions to 2^x-3x-1=0 (transcendental equation)
finally 0^0 approaches 0 after 6 years!
Переглядів 451 тис.7 місяців тому
finally 0^0 approaches 0 after 6 years!
I want all trig functions in one integral!
Переглядів 618 тис.7 місяців тому
I want all trig functions in one integral!
Berkeley Math Tournament calculus tiebreaker
Переглядів 88 тис.7 місяців тому
Berkeley Math Tournament calculus tiebreaker
I integrated the quadratic formula
Переглядів 408 тис.7 місяців тому
I integrated the quadratic formula
the first 5 days of calculus 2 but the integrals get harder!
Переглядів 61 тис.8 місяців тому
the first 5 days of calculus 2 but the integrals get harder!
limit of 1/(1-cos(ln(sin(tan^-1(e^(x^2)))))) as x goes to infinity
Переглядів 35 тис.8 місяців тому
limit of 1/(1-cos(ln(sin(tan^-1(e^(x^2)))))) as x goes to infinity
I don't even know why I'm watching this.
Tried solving using desmos. Plotted x+y=8 first. Then plotted x^y = some constant b. The value of b where the two graphs only have one point of intersection is the maximum value of the function, and that came out to be approximately 280.902799
Isnt last one sin(π/2+2πk) which always will give one and sin(-3π/2+2πk) which will also end on the positive side of the circumference as its going to the negatives and then the postives? Reasoning like that it would be 1+1 =2
guys jokes aside but how do you know that the limit of a continuous function is a function of the limit of the thing inside it? Is it calc 1 or 2 or 3? I dont remember getting this property when learning limits. Tanks
log base 1 does not exist...
Sir videos help me a lot to make my concept very strong in mathematics love from India❤❤❤❤
The easiest way to calculate sin 15 is sin (45-30) = sin 45cos 30 - cos 45sin 30. 45 and 30 are special angles.
If in doubt iterate! Here are 2 iteration equations for 2 real roots anyway. Use x = 1 to start things off x^5 - 5x + 3 = 0 x^5 = 5x - 3 x = (5x - 3)^(1/5) 1.275 682 204 x^5 - 5x + 3 = 0 x^5 - 5x = -3 x(x^4 - 5) = -3 x = -3/(x^4 - 5) 0.618 033 988 8 (Golden Mean)
I have a question, arctan (♾️) is not only equal to π/2, it also can be 5π/2, how do you prove that π/2 is the unique answer? Thanks
I’m too late for this but ever considered adding sinh(x) cosh(x) tanh(x) coth(x) etc, to the integral?
I like how my professors doesn't taught me this 🙃 Thank you professor, you are very useful
11:41
For each of them you could just multiply both sides by (x-1) for instance: (x-1)(x³+x²+x+1) = (0)(x-1) x⁴-1 = 0 x⁴ = 1 and therefore x = 1 ∠ θ Where θ = 0°,90°,180°,270° Except when θ = 0 we would have x = 1 which is an artifact created when multiplying by x - 1 and not a genuine solution
hey man how did you derive the 2 equation i am having a lot of trouble understanding that . how did you remove mod from the equvalence and all that
√i = √me if you square bothe sides i = me. Therefore i am me.
we can solve by adding the equations xy+z=40 eq1 xz+y=51 eq2 x+y+z=19 eq3 on adding eq. 1,2,3 x+xy+xz+2y+2z=110 adding 2 on both the sides x(y+z+1) 2(y+z+1)=112 (x+2) (y+z+1)=112 -------equation 4 from equation 3 y+z=19-x substituting y+z=19-x in eq. 4. (x+2) (-x+20)=112 -x^2+18x-72=0 (x-6)(-x+12)=0--------equation 5 from equation 5 x=6, x=12 substituting x=6 in equations 1,2,3 we get 6y+z=40--eq6 6z+y=51---eq7 6+y+z=19 --eq8 from equation 8 y+z=13 from equation 6 z=40-6y substituting z=40-6y in eq. 8 -5y=-27 y=5.4 substituting y=5.4 in equation 8 z=7.6
I found this formula through recursion once, and also number of squares
you didn't miss a single step, it got way easier to understand
I saw the blue pen 😂
Wow, I'm really glad I watched that video on Euler's equation, otherwise this video would be gibberish.
Welcome
Pls make the proof for sqrt of a+sqrt of a - sqrt of a so on
When you really really love this question
You should try the 2011 IMO question number 2 it is very fun
Somewhere around 24/25
All 5 solutions of the original equation (0, two positive and two negative) are valid. For angles: { 0, 36, 72, 108, 144 } + k * 180 for integer k including zero. For an even k they are 0 or positive and for an odd k they are 0 or negative.
why cant you just write the sin(x) as cos(x-pi/2)
within like 5 seconds of me thinking about it, I was like "y=1" but was also like "that is definitely correct, but way too simple for this to be the answer he gives" lol
Feynman's Trick or Leibniz Rule ?
This is very brilliant
Thanks!!
It's not that hard, it's just a sector of a circle = (1/3)pi×4^2 MINUS Area of triangle= (1/2)absinC = (1/2)×4^2×sin120 = 8×sqrt(3)/2 = 4sqrt(3) Then just a full circle minus 4 of those D shapes, easy.
I think the first step is the reason why this equation truly does not have a solution as a logarithm to the base 1 is not defined (not even in the complex world)
I was part of the year this question was on 😭
i = EXP(i*Pi/2) or i = EXP(i*(Pi/2+2*Pi)) --> SQRT(i) = EXP(i*Pi/4) or EXP(i*5*Pi/4) --> SQRTi) = Cos(Pi/4) + i Sin(Pi/4) or Cos(5*Pi/4) + i Sin(5*Pi/4) --> SQRT(i) = SQRT(2)/2 + i * SQRT(2)/2 or SQRT(i) = -SQRT(2)/2 - i * SQRT(2)/2
3:32:45 tan θ is wrong, you forgot thats 4x not 4
U r so smart Thank you 💗
11:55 that transition
george washington
I need this calculateor please🙏
OMG, seeing these questions bring me back memories of me sitting in front of the desk in my room, doing past papers after past papers. Just missed mine by 6 years (Jun 2016)
I know I am 5 years late for the party, but shouldn't integral number 31. equal to: -4*sqrt(1-sqrt(x)) + C?
This video deserves the word "ultimate"
i was having a hard time reviewing my instructor's pdf, thank you for this!~
∆ABC, AB=AC=1 and ∠A=36° Let D is on AC such that AD=BD then ∠BDC=∠C=72° and ∆ABC~∆BCD (AA) Let AD=BC=a ( cos72°=√[1-(a/2)²] ) then 1:a=a:(1-a) => a²=1-a => a=(-1+√5)/2 Thus cos72°=√(a+3)/2 =√[2(5+√5)]/4
Thank u sir
The no.1 confused me b/c I interpreted log as base 10. Also why do they make ln notation if people still use log for ln anyway?
This video 'I hate internet math' by doorwaydude is what I consider to be a 'sequel' to this vid. It attempts to explain why these debates exist in the first place (and why some of them are pointless). I really think people in this comment section should have a look if they are still unsure about things like 0.999...=1
Thanks, dude! 👍 No problem with dude, I hope?
So it doesn't change the fact that I don't like minus and I remove it, and I am still correct
But wait what about limits like lim(1/x) as x->0? From one side it approaches +inf and from another -inf. L'Hopital would say it's equal to 0 but I think most people would still say it's undefined/indeterminate?
Find Sin(1), multiply by 72 and you're set! /s