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Dr. Ebrahimian
United States
Приєднався 1 тра 2008
A place to learn problem solving strategies on a wide range of math topics.
Dr. Ebrahimian is a Math Professor at the University of Maryland, College Park and a Math Competition Coach.
- Coach of the University of Maryland Putnam Math Competition Team.
- Led the University of Maryland Putnam Team to fourth place after MIT, Harvard, and Stanford.
- Chair of the University of Maryland High School Math Competition.
Helping students achieve their goals, one student at a time.
For suggestions, comments and individual training requests please use the email listed below.
Dr. Ebrahimian is a Math Professor at the University of Maryland, College Park and a Math Competition Coach.
- Coach of the University of Maryland Putnam Math Competition Team.
- Led the University of Maryland Putnam Team to fourth place after MIT, Harvard, and Stanford.
- Chair of the University of Maryland High School Math Competition.
Helping students achieve their goals, one student at a time.
For suggestions, comments and individual training requests please use the email listed below.
A Geometry/Calculus Combo Problem, VTRMC, 2000
I go over a Geometry/Calculus Problem from the 2000 Virginia Tech Regional Math Contest.
Video Notes: umd.box.com/s/0lov00imy19tzlqpfyyzlpx75n5oyoqz
Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html
IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html
Putnam 2023:
A1: ua-cam.com/video/1BePT-p7uUg/v-deo.html
A2: ua-cam.com/video/7KnpgChlUc0/v-deo.html
A3: ua-cam.com/video/TpWiUiupvmU/v-deo.html
B1: ua-cam.com/video/iWnVKW0_zpw/v-deo.html
B2: ua-cam.com/video/xn1cgRkFjZM/v-deo.html
Putnam 2022:
A1: ua-cam.com/video/_68tK5AOm7c/v-deo.html
A2: ua-cam.com/video/RPXpmsLDipA/v-deo.html
A3: ua-cam.com/video/18W04FaBYnY/v-deo.html
A4: ua-cam.com/video/-54hO49i6xI/v-deo.html
B1: ua-cam.com/video/9SUMattI5MI/v-deo.html
B2: ua-cam.com/video/-q3cvHNzbaY/v-deo.html
B3: ua-cam.com/video/-faEWVZ8Q-w/v-deo.html
Putnam 2021:
A1: ua-cam.com/video/mIowvlzeRa0/v-deo.html
A2: ua-cam.com/video/JX5JkDts_x8/v-deo.html
Putnam 2019:
A3: ua-cam.com/video/yzexJpSg3ZM/v-deo.html
A4: ua-cam.com/video/PSpsGfF2AC4/v-deo.html
Putnam 2018:
B3: ua-cam.com/video/GK7UjqXDkbQ/v-deo.html
Putnam 2016:
A3: ua-cam.com/video/qLlJmUe2nk8/v-deo.html
Putnam 2015:
B4: ua-cam.com/video/XN2hc_ytY_M/v-deo.html
Putnam 2010:
A3: ua-cam.com/video/KHX5y8Y30hs/v-deo.html
Putnam 2003:
A2: ua-cam.com/video/NgZNMXG-C28/v-deo.html
A4: ua-cam.com/video/YNBmI_GxjhU/v-deo.html
Putnam 1999:
A4: ua-cam.com/video/JXCC6cwjbQY/v-deo.html
A6: ua-cam.com/video/ILOUApHat5k/v-deo.html
B6: ua-cam.com/video/4i7ycBJ5tj8/v-deo.html
Putnam 1998:
A2: ua-cam.com/video/2TmQpc9FNmE/v-deo.html
Putnam 1993:
A1: ua-cam.com/video/ogiz3OWYWgc/v-deo.html
Putnam 1992:
A1: ua-cam.com/video/h-ezDfBzWQY/v-deo.html
A4: ua-cam.com/video/Ml5oZZwoxWU/v-deo.html
Putnam 1989:
A1: ua-cam.com/video/cfm0DIdM4E8/v-deo.html
A3: ua-cam.com/video/7akt9pQF52w/v-deo.html
B2: ua-cam.com/video/V5iXpYj5gl0/v-deo.html
B4: ua-cam.com/video/JKVWazJ8TFw/v-deo.html
Putnam 1985:
A1: ua-cam.com/video/JHY-OmxByyI/v-deo.html
A2: ua-cam.com/video/iVpEm2OnE_Y/v-deo.html
Putnam 1980:
A3: ua-cam.com/video/mbZYdKM47BA/v-deo.html
Putnam 1976:
B5: ua-cam.com/video/kBuQjmijKG8/v-deo.html
ua-cam.com/video/P5Y_Bs8DbCk/v-deo.html
Putnam 1960:
B2: ua-cam.com/video/Mx42TXL12zU/v-deo.html
Video Notes: umd.box.com/s/0lov00imy19tzlqpfyyzlpx75n5oyoqz
Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html
IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html
Putnam 2023:
A1: ua-cam.com/video/1BePT-p7uUg/v-deo.html
A2: ua-cam.com/video/7KnpgChlUc0/v-deo.html
A3: ua-cam.com/video/TpWiUiupvmU/v-deo.html
B1: ua-cam.com/video/iWnVKW0_zpw/v-deo.html
B2: ua-cam.com/video/xn1cgRkFjZM/v-deo.html
Putnam 2022:
A1: ua-cam.com/video/_68tK5AOm7c/v-deo.html
A2: ua-cam.com/video/RPXpmsLDipA/v-deo.html
A3: ua-cam.com/video/18W04FaBYnY/v-deo.html
A4: ua-cam.com/video/-54hO49i6xI/v-deo.html
B1: ua-cam.com/video/9SUMattI5MI/v-deo.html
B2: ua-cam.com/video/-q3cvHNzbaY/v-deo.html
B3: ua-cam.com/video/-faEWVZ8Q-w/v-deo.html
Putnam 2021:
A1: ua-cam.com/video/mIowvlzeRa0/v-deo.html
A2: ua-cam.com/video/JX5JkDts_x8/v-deo.html
Putnam 2019:
A3: ua-cam.com/video/yzexJpSg3ZM/v-deo.html
A4: ua-cam.com/video/PSpsGfF2AC4/v-deo.html
Putnam 2018:
B3: ua-cam.com/video/GK7UjqXDkbQ/v-deo.html
Putnam 2016:
A3: ua-cam.com/video/qLlJmUe2nk8/v-deo.html
Putnam 2015:
B4: ua-cam.com/video/XN2hc_ytY_M/v-deo.html
Putnam 2010:
A3: ua-cam.com/video/KHX5y8Y30hs/v-deo.html
Putnam 2003:
A2: ua-cam.com/video/NgZNMXG-C28/v-deo.html
A4: ua-cam.com/video/YNBmI_GxjhU/v-deo.html
Putnam 1999:
A4: ua-cam.com/video/JXCC6cwjbQY/v-deo.html
A6: ua-cam.com/video/ILOUApHat5k/v-deo.html
B6: ua-cam.com/video/4i7ycBJ5tj8/v-deo.html
Putnam 1998:
A2: ua-cam.com/video/2TmQpc9FNmE/v-deo.html
Putnam 1993:
A1: ua-cam.com/video/ogiz3OWYWgc/v-deo.html
Putnam 1992:
A1: ua-cam.com/video/h-ezDfBzWQY/v-deo.html
A4: ua-cam.com/video/Ml5oZZwoxWU/v-deo.html
Putnam 1989:
A1: ua-cam.com/video/cfm0DIdM4E8/v-deo.html
A3: ua-cam.com/video/7akt9pQF52w/v-deo.html
B2: ua-cam.com/video/V5iXpYj5gl0/v-deo.html
B4: ua-cam.com/video/JKVWazJ8TFw/v-deo.html
Putnam 1985:
A1: ua-cam.com/video/JHY-OmxByyI/v-deo.html
A2: ua-cam.com/video/iVpEm2OnE_Y/v-deo.html
Putnam 1980:
A3: ua-cam.com/video/mbZYdKM47BA/v-deo.html
Putnam 1976:
B5: ua-cam.com/video/kBuQjmijKG8/v-deo.html
ua-cam.com/video/P5Y_Bs8DbCk/v-deo.html
Putnam 1960:
B2: ua-cam.com/video/Mx42TXL12zU/v-deo.html
Переглядів: 221
Відео
Putnam 1999, A6
Переглядів 45919 годин тому
I go over Problem A6 from the 1999 Putnam math competition. Solving Linear Recursions with Constant Coefficients: ua-cam.com/video/YtZhJYcww1o/v-deo.html Video Notes: umd.box.com/s/0lov00imy19tzlqpfyyzlpx75n5oyoqz Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html Putnam 2023: A1: ua-cam.com/video/1BePT-...
Placing Letters "X" and "O" on a Plane
Переглядів 18514 днів тому
Can we place an uncountable number of X's on a given plane? How about the letters O?
Putnam 1993, A1
Переглядів 1 тис.14 днів тому
I go over Problem A1 from the 1993 Putnam math competition. Video Notes: umd.box.com/s/0lov00imy19tzlqpfyyzlpx75n5oyoqz Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html Putnam 2023: A1: ua-cam.com/video/1BePT-p7uUg/v-deo.html A2: ua-cam.com/video/7KnpgChlUc0/v-deo.html A3: ua-cam.com/video/TpWiUiupvmU/...
IMO 2005, Number Theory Shortlisted Problem
Переглядів 709Місяць тому
I go over a number theory problem from the 2005 International Math Olympiad. I discuss the thought process behind my solution to this math competition problem. Video Notes: umd.box.com/s/0lov00imy19tzlqpfyyzlpx75n5oyoqz Number Theory Problems: ua-cam.com/play/PLvt4fmEPBjqqo1vWED0EvXdp9w2dvSFS5.html IMO Problems: ua-cam.com/play/PLvt4fmEPBjqrMFbipuG0ounTg0BivlWQ2.html Putnam Problems: ua-cam.com...
Putnam 1998, A2, A Geometry Problem in Two Ways.
Переглядів 307Місяць тому
I go over Problem A2 from the 1998 Putnam math competition. I provide two solutions to this geometry problem. One requires calculus while the other is a pre-calculus solution. Video Notes: umd.box.com/s/0lov00imy19tzlqpfyyzlpx75n5oyoqz Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html Putnam 2023: A1: u...
Putnam 2021, A2; A Limit Problem from the 2021 Putnam Math Competition
Переглядів 968Місяць тому
I go over Problem A2 from the 2021 Putnam math competition. This is a calculus problem with a relatively standard solution. Video Notes: umd.box.com/s/0lov00imy19tzlqpfyyzlpx75n5oyoqz Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html Putnam 2023: A1: ua-cam.com/video/1BePT-p7uUg/v-deo.html A2: ua-cam.co...
Why is This Product a Perfect Square?
Переглядів 5024 місяці тому
Everything you need to know about Complex numbers in math competitions: ua-cam.com/video/lldMQI4oC2w/v-deo.html Finding sums and products: ua-cam.com/video/EnZPCahdzeQ/v-deo.html ua-cam.com/video/EUzbolXDjwY/v-deo.html ua-cam.com/video/bkhOuDXeulU/v-deo.html
Sequence of Polynomials
Переглядів 9424 місяці тому
Is there a sequence a_n where every polynomial a_nx^n ... a_0 has n distinct real roots? Polynomial Problems: ua-cam.com/play/PLvt4fmEPBjqpqJctjtht5OKJDcIzXt3GP.html High School Math Competition Prolems: ua-cam.com/play/PLvt4fmEPBjqp_F7WsluzHPg8nDzutz4hO.html Algebra Problems: ua-cam.com/play/PLvt4fmEPBjqoERmGfnMu91qT-ebvWH5BB.html Sequence Problems: ua-cam.com/play/PLvt4fmEPBjqq5-XHriERcUoTA8M...
A Diophantine Equation with a Slick Solution
Переглядів 1,6 тис.5 місяців тому
I go over a problem from 2008 Polish Math Olympiad. IMO Problems: ua-cam.com/play/PLvt4fmEPBjqrMFbipuG0ounTg0BivlWQ2.html Number Theory Problems: ua-cam.com/play/PLvt4fmEPBjqqo1vWED0EvXdp9w2dvSFS5.html High School Math Competitions: ua-cam.com/play/PLvt4fmEPBjqp_F7WsluzHPg8nDzutz4hO.html
Putnam 2023, B1; Interesting Combinatorics Problem from the 2023 Putnam Math Competition.
Переглядів 8286 місяців тому
I go over Problem B1 from the 2023 Putnam math competition. This is a combinatorics problem with a clever solution. Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html Putnam 2023: A1: ua-cam.com/video/1BePT-p7uUg/v-deo.html A2: ua-cam.com/video/7KnpgChlUc0/v-deo.html A3: ua-cam.com/video/TpWiUiupvmU/v-de...
A Very Difficult Inequality Problem with an Elementary Solution
Переглядів 8286 місяців тому
I solve a very challenging inequality problem form the University of Maryland High School Math Competition. Inequality Problems: ua-cam.com/play/PLvt4fmEPBjqrTh_CV1Ck3QP2jl5J4MAJA.html UMD Math Competition Problems: ua-cam.com/play/PLvt4fmEPBjqoBXi-QOyGzDbW-OCHJt0O8.html IMO Problems: ua-cam.com/play/PLvt4fmEPBjqrMFbipuG0ounTg0BivlWQ2.html
Putnam 2023, B2; A Neat Number Theory Problem from the 2023 Putnam Math Competition.
Переглядів 1,3 тис.6 місяців тому
I go over Problem B2 from the 2023 Putnam math competition. I discuss my thought process behind getting to a solution. Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html Putnam 2023: A1: ua-cam.com/video/1BePT-p7uUg/v-deo.html A2: ua-cam.com/video/7KnpgChlUc0/v-deo.html A3: ua-cam.com/video/TpWiUiupvmU/v...
Putnam 2023, A3; A Very Challenging Putnam Calculus Problem!
Переглядів 1,3 тис.6 місяців тому
I go over Problem A3 from the 2023 Putnam math competition. I discuss my thought process behind getting to a solution. This very challenging calculus problem is quite difficult to solve. In this video you will see what I try and how I end up with a solution. Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6....
Putnam 2023, A2; Solution to a Polynomial Problem from the 2023 Putnam Math Competition.
Переглядів 1,2 тис.6 місяців тому
I go over Problem A2 from the 2023 Putnam math competition. I discuss how such problems are generally approached and eventually present a solution to the problem. Putnam Problems: ua-cam.com/play/PLvt4fmEPBjqrtO0SCh43ob4mgWyh6amBm.html IMC Problems: ua-cam.com/play/PLvt4fmEPBjqr6Pk0QS7aKJSBUnBod7xQ6.html Putnam 2023: A1: ua-cam.com/video/1BePT-p7uUg/v-deo.html A2: ua-cam.com/video/7KnpgChlUc0/v...
Putnam 2023, A1; Solution to a Calculus Problem from 2023 Putnam Math Competition
Переглядів 2,3 тис.6 місяців тому
Putnam 2023, A1; Solution to a Calculus Problem from 2023 Putnam Math Competition
Can You Solve This Divisibility Problem Involving Combinations?
Переглядів 4646 місяців тому
Can You Solve This Divisibility Problem Involving Combinations?
Challenging Geometry Problem in Two Ways; 2023 UMD Math Competition, Part 2, Problem 2
Переглядів 2486 місяців тому
Challenging Geometry Problem in Two Ways; 2023 UMD Math Competition, Part 2, Problem 2
A Fun Combinatorics Problem; University of Maryland High School Math Competition, Part 2, Problem 2
Переглядів 2336 місяців тому
A Fun Combinatorics Problem; University of Maryland High School Math Competition, Part 2, Problem 2
A Counting Problem in Two Different Ways; IMC 2020, Problem 1
Переглядів 4106 місяців тому
A Counting Problem in Two Different Ways; IMC 2020, Problem 1
A Challenging Pigeonhole Principle Math Competition Problem!
Переглядів 1517 місяців тому
A Challenging Pigeonhole Principle Math Competition Problem!
A Very Challenging Number Theory Problem; Canadian Math Olympiad, 2021, Problem 4
Переглядів 7337 місяців тому
A Very Challenging Number Theory Problem; Canadian Math Olympiad, 2021, Problem 4
IMO 2005, Problem 4; An Interesting Number Theory Problem.
Переглядів 1 тис.7 місяців тому
IMO 2005, Problem 4; An Interesting Number Theory Problem.
A Challenging Algebra Problem; Putnam 2003, A4
Переглядів 1,2 тис.7 місяців тому
A Challenging Algebra Problem; Putnam 2003, A4
IMO 1987, Problem 4; A Challenging Functional Equation Problem.
Переглядів 1,1 тис.7 місяців тому
IMO 1987, Problem 4; A Challenging Functional Equation Problem.
A Surprisingly Challenging Quadratic Polynomial Problem
Переглядів 7207 місяців тому
A Surprisingly Challenging Quadratic Polynomial Problem
A Challenging IMO Functional Equation Problem, IMO 1977, Problem 6
Переглядів 9607 місяців тому
A Challenging IMO Functional Equation Problem, IMO 1977, Problem 6
Putnam 2021, A1; How Many Hops Does the Grasshopper Take?
Переглядів 9147 місяців тому
Putnam 2021, A1; How Many Hops Does the Grasshopper Take?
2023 AMC 12A; Solution to Problems 22, 23, 24, and 25
Переглядів 1,2 тис.7 місяців тому
2023 AMC 12A; Solution to Problems 22, 23, 24, and 25
If you set y(x)=AP and make a y substitution, the integral essentially becomes integral of 1dy from y=l1 to y= l2. Technically with my method you have to split the triangle into 2 right angled triangles ABM and ACM where M is the dropped perpendicular, and integrate over the 2 regions of x left and right of M
This is an interesting idea. I tried that but I don’t believe this is accurate. If I understand what you suggest correctly you claim that y’ is the same as cos(theta). Why is that true? My calculation in the video shows that’s not the case.
@@DrEbrahimian Since (x-m)^2 + h^2 = y^2, you get 2(x-m) = 2ydy/dx differentiating implicitly, so dy/dx = (x-m)/y = cos(theta). Its essentially the same method as you, just my y is your root(u)
@@rgqwerty63 oh wow. Thank you for sharing that. I didn’t realize the formula that I got does indeed show what you were saying! Thank you for this great insight!!
Induction is certainly a unique technique for this problem. But that 81/16 is a universal theme across the board for this problem.
Sir love from india i love your methods so much can u pls help in in solving a problem i have a major test on 5 pm today and noone is telling me how to solve this problem pls solve otherwise i will fail 😢😢 🙏🙏 Limit n approaching infinity 1/n.cosπ/n cos2π/n.cos3π/n......cosnπ/n Pls sir pls help me❤😢😢😢😢😢
At 13:33, are you sure it isn’t use r^n, nr^n, n(n-1)r^n, n(n-1)(n-2)r^n as many times as needed? I don’t think the text makes sense as when you differentiate exponents decrease by 1. Could you pls clarify?
Hi sir , I am a student about to enter 2nd year . I am very much Interested in International Mathematics Competition, But i am not fully aware of how to prepare for it ? I couldn’t find much online either . Can you help me sir ? . Is it possible to connect with you on LinkedIn ?
Yes, there aren’t too many resources for that. You can try my book: bpb-us-e1.wpmucdn.com/blog.umd.edu/dist/5/615/files/2024/01/Putnam_Guide.pdf
Masterful problem solving... Thanks! I learned a lot from this video.
Plz tell me how can u solved all problam what course are u did it
Hi sir I am 1st year university students I have no experience math competition in high now I'm study in university and I want to solve putnam problam can u recommended me what course and book learn first before the solve putnam question
I wrote a book on this that should help you. You can find it here: bpb-us-e1.wpmucdn.com/blog.umd.edu/dist/5/615/files/2024/01/Putnam_Guide.pdf
After reading this book, is it possible to easily solve Putnam questions directly?
@@NeerajKumar-gk9kz For this exam to become easy, reading just one book will not be enough, it is a long and hard process. I'm not trying to demotivate you but this is the truth
You didn't proof Os are uncountable, I didn't watch the rest.
As c ranges over all positive real numbers and the set of positive real numbers is uncountable, the number of O's is uncountable.
He did prove it. Awesome video. Very different problem.
Limit questions are beautiful please bring more
This is a typical jee adv question (India)
I believe you can also apply mean value theorem here. C= int|0-b (f(x) dx )/ b.
That’s a very interesting approach! Thank you for sharing that.
Nice vids man 👌🏽
Very clear and straightforward demonstration, thanks!
nice
You solve problems like a disciplined chess player. It is nice that you include your steps of thought along with the solution. This channel is a gem.
Nice work sir! Subscribed!
When p is a prime number In gcd(a,b) Can I solve it either a=tp, b=lp??? Gcd(tp,lp)
great method
you said ...we showed there does not exist more solutions ..how???
2:33 why isn't it when n is divisible by 4 ? (Instead of n is divisible by 2) edit : sorry you say it just after : bc a^2+1 isnt divisible by 4.
I see. clever work. 🙌
Please would you solve the problems of RMM 2024? 😊
Can you send me a link? I will take a look!
Thanks
Nice
How elegant!
Can this problem be solved using Fermat’s Little Theorem?
I doubt it!
Nice ❤ problem
An alternative reasoning to the geometric proof: Consider the same argument until 6:36, with no need of H. Create an auxiliary point S = (1,0) and take an angle α of the sector OSQ. By the previous conclusion at 4:12, we have that A_α + B_α = α; and A_(α+θ) + B_(α+θ)= α+θ. Subtract both equations, yielding A_(α+θ) - A_α + B_(α+θ) - B_α = θ. Now, doing a simple drawing of the regions of the equation, we easily conclude: A_(α+θ) - A_α = A_θ, B_(α+θ) - B_α = B_θ. Bring that up to the equation, resulting in A_θ + B_θ = θ, which is what we wanted to prove.
This is brilliant!
i came up with a completely different solution to this problem. at first the i noticed the f(x+y)=f(x)+f(y). since this is independent of position of arc. take a small angular element dx of the arc and find f(dx)=(dx(cosx))cosx+(dx(sinx))sinx=dx now we just have to add up all the small angles dx
Maybe I misunderstand what you are doing but how do you know the sum of the two areas is a function of theta? Isn’t that what we’re trying to prove?
I'm a 12th grader of India I don't know much about putnam examination, it is definetly hard but this question was not too complicated I was able to solve most it in my mind just from the thumbnail... And also your explaination was quick and simple😊
Yes, this one wasn't too complicated. Nice job!
I feel so smart because Squidward teaches me math.
Ahahahhaahhaahha
Thanks for posting again.... please do the last two problems (9 and 10) of IMC 2023.
Will try those!
Nice problem.I have only one question.How can I think about ln to solve this problem,or just because the expression is dealing with powers?
When dealing with indeterminate forms 0^0, 1^infty, infty^0 you would take natural log to evaluate the limit.
Sir please upload more problems
Send me suggestions if you wish. I’ll have more time once summer starts!
i have two pieces of advice: (1) don't skip too many steps; some steps are not as obvious for typical people and you should keep them in your demonstration (2) explain briefly the logic/thinking of this Cauchy Induction
how did we get derivative when 2 does not divide n
The coefficient of each term with odd exponent is zero.
always just 1 :)
Hello and thank you for the great explanation! I have just one question - at 24:06, what is the formula you use to calculate limit of v mk using the limit of u mk?
I use linearity of limits. Limit of a_n -b_n is the same as difference of limits of a_n and b_n.
lavn es qo arev. hamard tox shpvenq
@@DrEbrahimianThanks jigyar
Xndrem harazat
@davsahakyan_ I am curious: what language is that? Armenian?
Superb sir 👌
not even national level last 2 or 3 questions in most countries.
hey i have a doubt! in 4:24 , while writing the expression for Sn+1 in terms of union , we have A belongs to Sn right? but Sn also has many other elements , so what about their union with {Xk} ?
If a set has size at most n+1, i.e. it is in S_{n+1}, then it can be written as the union of a set with at most n elements and a singleton.
I think in 9:30 the ineaquality should be a<b<a+ε right?
True! Thanks for catching that!
Titu generalizes this to the case in which positive even integer k is in place of 1987. The number of such function is k!/(½k)!, so there are no such functions for odd k
Thank you for sharing this. This is very interesting.
f : ℕ₀→ℕ₀ where ℕ₀=ℕ∪{0} f(f(n))=n+k f(n+k)=f(f(f(n)))=f(n)+k thus, f(n+qk)=f(n)+qk for any integer q All is left is to check the values of f for n∈{0,1,...,k-1}=ℤₖ suppose t∈ℤₖ f(t)=qk+r, for some r∈ℤₖ t+k=f(qk+r)=qk+f(r) t-(q-1)k=f(r)≥0 (q-1)k≤t<k q-1<1 ⇔ q<2 ⇔ q∈{0,1} This defines ordered pairings in ℤₖ, that is (r,s)⇔f(r)=s⇔f(s)=k+r It is easy to see that there are k!/(½k)! such pairings(functions)
is this the problem where you pick median point to minimize total distance
Yes!
What if u don't do p=|p|?
You could still solve the problem. You need to calculate the product of powers of e separately.
very good video!