#competition-math
1 messages · Page 6 of 1
no worries!
hi everyone
What
as in the international maths olympiad?
yahh
i almost made it to the team for the internationals but i didn't quite make it
anyway i'm at uni now so i can't do the IMO anymore
r u preparing for IMO?
wait r u talking about that one random indian thing called the IMO even though it is not international nor an olympiad?
haven't started studying for it yet
i dont really know much about it tbh
send me what ur taking about cus the actual international maths olympiad happened a few months ago in the UK already
ahh okay
the next one is in australia and won't be held until next summer
Yes, that's correct! The International Mathematical Olympiad (IMO) is held annually, but the dates can vary from country to country. In the UK, the selection rounds and national competitions leading up to the IMO are often completed before the international event takes place, allowing the selected team to prepare for the IMO.
In India, the selection process typically involves multiple rounds, including regional and national competitions. The INMO (Indian National Mathematical Olympiad) is usually held a bit later in the year, which means that students in India may still be in the process of preparing for their selection to the IMO team when the event has already occurred in other countries.
what was your score?
i didn't do the IMO
oh
damnn mann you must be smart
got any tips?
ngl i'm still slightly confused by what ur asking abt
are u saying ur preparing for the regional olympiads in u area?
ic, well gl for those!
there's a discord server called maths olympiad discord server which is better suited for maths olympiad questions
ohh thanks for letting me know , i'll join it 😄
problems, problems, and problems
problems like these:
but easier
try looking for math olympiad problems more your style
like AMC or something easier like comps from big companies that steal your money
ohh thanks dude : ) , but when i'm trying to do problem and i am stuck at them i lose all the motivation to do so
just do problems from AoPS, since they give out solutions, dont do IMO problems from AoPS tho since most of them are above your level
just do other problems since they have a whole library of past olympiads
man thank you very muchh!
hey do you got any book suggestions?
i only practice online
if i were to recommend a book for you maybe some basic fundamentals in olympiad math
oh also forgot to mention you should prioritize proofs
most problems are asking you to give proof
ok bye
like proving theorems etc?
Hi guys
International maths Olympiad?
it may have been a 'legendary' problem back in 1988
but it's really not that hard in the modern olympiad landscape
dude if thats not a legendary problem then i’m a kindergartener
sorry i didn't mean legendary sarcastically lol
basically this question was hard bcus u had to come up with the idea of vieta jumping to solve it
that was a very novel idea that no one had done before
but then basically "oh look that's a cool olympiad trick" and now suddenly you have a billion questions that all use vieta jumping
it's not hard in the modern landscape cus basically ppl overused the idea
to the point where it's more "oh look another vieta jumping question" rather than "damn how do u do this"
wot is vieta jumping
I only know vieta’s formula or whatever and i know that probably is not related at all to “vieta jumping”
questions like IMO 2007 Q3, IMO2007 Q6, IMO 2020 Q6 are considered the hardest IMO qs in recent history
basically it's the trick to do IMO 1988 Q6
do u compete in imo
the rough tldr is that this question was really hard but only had 1 trick
then ppl came up with a load of other questions that all use the same trick
So its hella easy if you know the trick but impossible if you dont
but if u have a bunch of questions that have the same trick, it eventually becomes 'learn the trick' rather than 'come up with the trick'
hope that explanation makes sense
yh
the main thing is ppl overused it so it got really boring
I feel dumber every day I am in this server
almost
I should leave so my ego regains
didn't quite make the IMO team for my country but i got to the final stage
dude how are u so smart wwttthhh
ahaha yeah it can feel like it sometimes
lol ty <3
i'm sure u're smart as well
are u in college yet
given that u recognised the problem source
i am dumb as hell
yh i'm at uni now so i can't compete in these things anymore
back to get my ego destroyed more, what is 1 + 1
what's that? is that the national olympiad for your country
could you dm me the link 🙏
what country would u have represented if you were selected?
How do I get faster with calculation?
Should I focus on techniques, training, or working memory?
any hints plzz
tf
,w sum n/(n^2 + 2kn + k^2) from k = 1 to n
what to compare to hmmm
+ig s infinity
Thats just a riemann sum no?
oh RIGHT
Ye so its just integral of 1/(t²+t+1) from 0 to 1
,w integrate 1/(t²+t+1) from 0 to 1
So that
wait
yeah it has to do with the summation bounds
Yea that
But well n is not approaching infinity so i got no clue
1/(x^2 + x + 1) is a decreasing function in [0, 1] so the left Riemann sum will be larger than the integral
but the right Riemann sum will be smaller than the integral
the left Riemann sum is T_n and the right Riemann sum is S_n
that makes perfect sense now that I know the answer lol
also yeah we are not taking the limit, so the sum will be a finite number of rectangles
Um what 💀 like since Sn = Tn + something shouldnt Sn be greater
The Tn is not a proper riemann sum tho i think?
Everywhere it says n
It should be n-1
I think
nah, the variable in both summations is the k, so it's fine
basically you know Tn is the left Riemann sum cause it's from k = 0 to k = n - 1
the right Riemann sum would range from k = 1 to k = n
both have n rectangles
okok
whats left ansd right reimann sum
Helppp plss
I don't quite understand how I could turn gcd or lcm into a variable in this
you probably need the fact that ab - a - b + 1 = (a - 1)(b - 1)
so add 1 to both sides
I'm not sure how to proceed
hint: write a = dx, b = dy where d=gcd(a,b)
the final stage of TSTs for my country, doesn't really have a name
like only ~10ppl take it, it's not really a stage of our national olympiads
Can you please explain it to me
it's quite a common trick to rewrite our variables a,b
in terms of a/gcd(a,b), b/gcd(a,b) cus then they're coprime
anyway so let's call gcd(a,b) = d
then write a = dx, b = dy
then we know gcd(a,b) = d and lcm(a,b) = dxy
etc.
nw!
I'm sorry for asking again, for my question I change all of a into dx and b into dy
So I write it again as
D^2xy -dx-dy = d+dxy
After that I make
D^2xy = d(x+1)(y+1)
Then I cross the d
Dxy=(x+1)(y+1)
Then I got stucked
Did I do something wrong here
@high goblet tyy
so there's possible another way to finish from here
but my thought process was to write it as
d = (x+1)(y+1)/xy
i.e. (x+1)(y+1)/xy is an integer
this is a useful condition - why?
Cuz we may find d from there
I'm lost bro
well intuitively
if x=100 and y=100
then (x+1)(y+1)/xy is just very slightly larger than 1
and definitely smaller than 2
and certainly not an integer
in fact for a lot of values of x,y, this is between 1 and 2
so let's wlog x <= y
can u find a restriction on x?
if x>=3, what can u say about (x+1)(y+1)/xy
4(y+1)/3y at max
I'm truly lost here
LY
can u use this to finish off the problem?
Alr let me tryy
By the way @high goblet why did you use x>= 3 and y>=3 why Did you use 3 in here
guess
(maybe if x>=3 then we can force it to be less than 2)
(oh it works)
as in this is quite a common trick that appears in quite a few questions
you get an expression that has to be an integer
but isn't likely to be an integer for very many values of x,y
because you can bound it between i.e. 1 and 2 for a lot of values of x,y
then wlog x <= y
and take a guess for x (i.e. x>=3)
then if that inequality works, you know x=1 or x=2
otherwise if you couldn't establish a useful ineq.
try x>=4 etc.
Ohh I see can you continue solving it so I can review it and potentially understand it
i mean u should be able to finish it off right?
we have x=1 or x=2 now
try to finish from there
Alr
yh so i believe it's the same trick for this q
and this q
@high goblet is there a name for this trick so I can learn it
not really?
bounding?
finding inequalities to bound a quantity is very common and comes up like everywhere
For x = 1 there is no suitable y because 2(y+1)/y <= 16/9
Dividing both by 2
(Y+1)y <= 8/9
Not possible for positive integer
Is this explanation right??
well no that's not what's going on
💀
^
so we've said that (x+1)(y+1)/xy is an integer
Alr ty let me try to do it
if x>=3 then y>=3 so that is between 1 and 2, a contradiction
so we need to test x=2 and x=1
And after I check it
What should I done
This material is beyond my level rn
I join some math competition but never see this material come out
i think it might be helpful to try to understand the solution
Write $a=dx, b=dy$ where $d=gcd(a,b)$. Then our equation becomes:
$$d^2xy - dx - dy = dxy + d$$
i.e.
$$d = (1+\frac{1}{x})(1+\frac{1}{y}) \in \mathbb{N}$$
Clearly $(1+\frac{1}{x})(1+\frac{1}{y}) > 1$. Now wlog $x\leq y$. Then if $3 \leq x \leq y$ then
$$(1+\frac{1}{x})(1+\frac{1}{y}) \leq (1 + \frac{1}{3})(1 + \frac{1}{3}) = \frac{16}{9} < 2$$
and so is clearly not an integer. Thus, $x=2$ or $x=1$. \
If $x=2$ then $\frac{3}{2}(1+\frac{1}{y}) \in \mathbb{N}$. If $y > 3$ then we get another contradiction and thus $y=3$, giving us $d=2, x=2, y=3$ as a possible solution. \
If $x=1$ and $y \geq 3$ then
$$2 < 2(1+\frac{1}{y}) \leq \frac{8}{3} < 3$$
and so not an integer. Thus, $y=1$ or $y=2$. It is trivial to see that these work and thus $x=1, y=1, d=4$ and $x=1, y=2, d=3$ are 2 further possible solutions. \
Hence, the solutions to our original quesiton are $(a,b) = (4, 6), (6, 4), (4, 4), (3, 6), (6,3)$
LY
nw
Bruhhhh
That is whyy
I understand
I make the x a internet but I didn't make sure the original "a" variable also an interger
Oooh I forgot
Can anyone explain me how should I try to approach the number 2 question about 100 digit real number
you wanna make the sum of the digits nice
fix the sum of the digits then try to find a number that satisfies the properties you want
remember that we don't really have any good ways to test if i.e. n is divisible by 19 etc.
so u want to make the sum of the digits nice
think about how u can do that
Alr
I make number where the sum of the digits will be 125
1......125
I though it would work
@high goblet
Where there is 96 spot left for the rest of the number
This is the 100 digit number
yh that works
u just have to fudge ur numbers a bit
so that the sum of the digits is 125
Sum of squares is usually destroyed by Cauchy Schwarz
this when it's on the larger side of the inequality though (in this case it is so no problem)
Cauchy Schwarz:
[\left(\sum_{i=1} u_i v_i\right)^2\le \sum_{i=1}u_i^2\sum_{i=1}v_i^2]
Then take $v_i=1$ and $u_i$ as in the sum they showed, then rearrange.
Max
Alr let me try it
Hello guys
I need references for which book I can use for Maths for class 12th boards?
How do I actually learn from my mistakes? I understand how to solve that particular problem now, but couldn’t apply the exact same thing in a different context
wat
can you elaborate further
your description is kind of weird
sorry, just cant understand
Sorry I'm kinda lost here
I'd multiply both sides by (a+b) since that seems potentially interesting
has anyone here done the official aops amc12 mocks
how does it compare with actual amc12 in terms of difficulty
well I guess we know it's some conic section, and it's symmetrical across the line a=b. Solving gets us 2 points, so that means it's either an ellipse (good finitely many things to check) or a hyperbola (boo infinitely many things to check). We know it's not a hyperbola because... well I just checked the points at infinity in the projective plane but probably less fancy way to do this by trying to find asymptotes or something.
of course this is all ad hoc rationalization, I just graphed it in desmos lol
Then I used quadratic formula
Then just found x and y
X = a, b=y
can you elaborate on this step
There
So there is 6 pair
How should I try to approach this question
- Note that $$(ad-bc)^2=(a^2+b^2)(c^2+d^2)$$
Civil Service Pigeon
nah the questiobn all clear to me
can some one just solve thje first question
q1
Does my question here could use Cauchy schwarz too
.
As in there’s no answer b/c ac never achieves a maximum
Please do not ping individual helpers unprompted.
what abotut thw seconfd question the question in which ac + bd is min
Nah I tried it yesterday, Cauchy Schwarz reduces it too much
(once you apply CS and remembering you can choose the different letters arbitrarily, you can essentially show the minimum of the expression is 0, which is too low)
yh
first expand out our entire thing
often in inequalities, you have something that looks nice, but often the first step to solving it is just to expand out
anyway u end up with this
this looks horrific
partially because we have ws multiplied with xs and ys but not zs etc. etc.
can u rewrite this in a nicer way?
then u can apply C-S and finish
Ly saving me once again
What do you mean nicer way
Like give me a hint how to use Cauchy schwarz in here
well this was actually kinda a hint
notice that w^2 is multiplied by x^2 and y^2
and z^2 is multiplied by x^2 and y^2
anyway stare at it and realise that we have
(w^2 + z^2)(x^2 + y^2) + 2wx + 2yz + 2 >= 1
now u can CS that
Find all natural numbers (a,b) such that ab| a^2024 + b. Can anyone help me with this??
funnily enough someone posted this problem earlier today lol
(a,b) = (1,1)
anyway the idea here is clearly:
a | a^2024 + b
so a | b
Maybe thats the ans
then if a | b write b=ab'
then a^2 | a^2024 + ab'
so a | b'
repeat that basically until u get a conclusion
I also got that but not in this way. Can you explain this step?
Oh i see
does anyone have any tips on studying for short-answer contests? aka for getting faster and doing less mistakes
short answer as in a short statement or just a number?
I mean those boring ass contests with like 20 questions for 3 hours yk
its ok
i completed the square on the RHS, then multiplied everything by negative 1 to get ab-a-b=-(a-b)^2, then i added 1 to factor the LHS by sfft (simons favorite factoring trick). when we factor, we get (a-1)(b-1)=1-(a-b)^2. we factor RHS by difference of squares for (a-1)(b-1)=(1-a+b)(1+b-a). now we see that 1-a+b=a-1 and 1+b-a = b-1. solving the system of equations gives a = -2 and b = -2 which are the only ones i think (i could be wrong)
idrk if I should be asking this here, but is this channel used for discussion about how to solve comp questions (ie, the last 5 questions of AMCs) or just kinda talking about the comps in general
I joined like, five minutes ago so I know nothing 😭
both ig
alrightyy
starting with amcs is easy
just make an aops account and do the mocks and use their books
I took an aops class and I lowkey hated it
dang which one
i dont really remember, apart from the fact that it was on the amc10 and discussion strategies
I also did the seminar
oh amc 10 problem series probably
yeah probably that
I prefer face to face teaching, which was probably why it was so tedious
yeah
i havent done any classes yet but if you just use the books from aops (intro series and volume 1) and do questions it will boost your score
and also do mocks
are the books free??
no
you claim that 1-a+b = a-1 but why?
that doesn't follow from (a-1)(b-1)=(1-a+b)(1+b-a)
what contest r u exactly referring to?
i tried setting 1-a+b to b-1 but i got infinite solutions
idk i may be wrong
i think in general, u've probs just gotta do more qs to build up speed etc.
but yeah generally multiple choice qs don't really matter
idk how it works in the US system
me neither
ah k
two brazilian contests, jacob palis and obmep, but if you're not brazilian you prob have no idea what these are
ah kk
what r the questions like?
i think in general, just do qs
multiple choice qs are usually followed by like the harder more prestigious competitions anyway
do you think I should do like, them timed or just do one after the other
probably do them timed
yeah I really regret only practicing for the harder and cooler ones so that's why I'm kinda desperate for something rn
I thought if I just got really smart I would automatically think these contests are easy but they are not
I mean, each question is easy
ty
hum I'll find one with pretty median difficult of each contest
ok
how many ways can we color each labeled point with red, blue and green such that no 3 colinear points have the same color
eww trial and error
yeah probably just do questions to eventually build up speed
yeah it's honestly abhorrent
well from obmep every question is straight up extremely easy so it's REALLY just not getting anything too wrong or thinking too much
I'll send one that I could not solve fast because my brain hurt a little
Benício put together, twice, three dice in such a way that faces in contact have the same number, each time he summed the numbers in all faces that are not in contact and the difference between the sums was 16. which were the numbers in the faces that were never in contact?
quite saddening
maybe I'll do like a daily amount of questions or something as the actual shore it is
maybe weekly for flexibility idk
jesus christ these questions look like pain
can you translate to english
I did
to be fair obmep is meant for people with no experience in math to be incentivized to think about it in a more fun way
but for someone like me it's just painful I already know all the tricks
ic ic
+the standard is each school forcing all students to take it but my school doesn't do that so only 2 people per level can pass to the second phase which made me unable to do it this year
jacob palis is similar but in a higher level, it incentivizes people to start learning the first little olympiad basic tricks like cyclic quadrilaterals and stuff
`has anyone here done the official aops amc12 mocks
how does it compare with actual amc12 in terms of difficulty
they are very orz
x²+4y²+9z²-2x-12y+6z+10=0
Show that 1/3≤x+y+z≤4
x²+4y²+9z²-2x-12y+6z+10=0
⇔x²-2x+1+(2y)²-12y+9+9z²+6z=0
⇔(x-1)²+(2y-3)²+9z²+6z=0
⇔(x-1)²+(2y-3)²+9z²+6z+1-1=0
⇔(x-1)²+(2y-3)²+(3z+1)²=1
0≤(x-1)²≤1
⇔0≤|x-1|≤1
⇔|x-1|≤1
⇔-1≤x-1≤1 |+1
⇔0≤x≤2
⇔x∈[0;2]
0≤(2y-3)²≤1
⇔0≤|2y-3|≤1
⇔|2y-3|≤1
⇔-1≤2y-3≤1 |+3
⇔2≤2y≤4 |:2
⇔1≤y≤2
⇔y∈[1;2]
0≤(3z+1)²≤1
⇔0≤|3z+1|≤1
⇔|3z+1|≤1
⇔-1≤3z+1≤1 |-1
⇔-2≤3z≤0 |:3
⇔-2/3≤z≤0
⇔z∈[-2/3;0]
min (x+y+z)
=min x+min y+min z
=0+1-2/3
=1/3
max (x+y+z)
=max x+max y+ max z
=2+2+0
=4
⇒ 1/3≤x+y+z≤4
Nice
But you can use latex on discord
A lot easier than having to copy $\in$ and $^2$
Max
slightly easier imo
$$ 2^p \neq 3m + 1 $$ prove for positive odd integer values of p and m
Mr.Bombastic
Need help
without loss of generality, note that the inequality is homogenous, as in $(a,b,c) \mapsto (ka,kb,kc)$ for $k \in \mathbb R \setminus {0}$ doesn't change the inequality
higher's secret twin brother
so we can let $abc = 1$
higher's secret twin brother
AMGM gives $\ge 3 \left( \left| \frac{abc}{(b + c)(a + c)(a + b)} \right| \right)^{1/3}$
hmmmm
oh if you can show that (a+b)(b+c)(c+a) >= 8abc you're done
wait that's the wrong direction sorry
higher's secret twin brother
i dont know the original que
but this part is easy
just apply am gm in a, b then in b,c then in a,c
and multiply
I think we need another approach since the inequality is in the wrong direction
what was the original que
this?
lemme think
nvm i give up 💀 how would you even
that looks an awful lot like it need the GM-HM
but then there's inequality sign
nd HM is smallest of them all
you cant really compare
Approach Zero: A math-aware search engine.
oh the inequality isn't sharp
if in doubt just Approach0
thats cheating
true that
also comp maths people rarely give detailed solutions
you always have to fill in the gaps yourself
I agree
wow. Thanks a lot
I suppose (1+sqrt(5))(1-sqrt(5))=-4 is not a coincidence that 4 is in the denominator, idk
It is 🥶
you have the answer?
Yes I have a full solution
It's very long so there may be some error but I think I have the general idea
gotcha, yeah I guess there may be more than one way to do it, but if you didn't use that fact that's good to know
oh I think I see a way to do it
,texsp ||think we can replace the $a_k$ and $b_k$ with these then work out the geometric series we get, assuming they converge $$\sum_{k=1}^\infty \frac{\frac{(1+\sqrt{5})^k+(1-\sqrt{5})^k}{2} + (1+\sqrt{5})^k-(1-\sqrt{5})^k}{4^k}$$||
no idea if that actually spoilers the texit, I know there is/was a way for texit to spoiler and I have spoilers to auto-show
,texsp
Please give me something to compile, for example latex ,tex The solutions to \(x^2 = 1\) are \(x = \pm 1\).See ,help and ,help tex for detailed usage and further examples!
this is not spoilered
Merosity
that do it?
yep!
ty ty
nw i just learned abt it a couple days ago
Good luck computing that
it's really just 2 geometric series
Oh wait
it's not as bad as it looks
you can kinda work it through with +- on the sqrt too to get both in one go if you're really wanting to be cute
Yeah I think that works, but the idea that I thought was cool with that problem is you can actually find a closed form for a_i and b_i (Kinda)
If you want to try and solve it that way you can
By all means it's harder though
interesting, would be curious to know
well do we get the same answer I just worked it out and got -2/sqrt(5)
I wouldn't be surprised if I made a mistake though lol
I checked my longer solution through demos and stuff (because you can) and honestly, it would probably never have a radical form like that in the end I probably made a mistake too
binomial thm i think
I don't see how that gets us a closed form though
maybe the sums end up nice 
i dont see any other way to elementarily get a closed form
that was the first thing I did tbh but didn't see anything
then just noticed I could write a_k, b_k in terms of the exponentials so it'd all thread through the geometric series
so that's where I gave up, maybe some combinatorics trickery can be done though on those binomial coefficients
maybe we want to expand 5=(1+4) and do another binomial expansion there, cause, idk 4
swap the sums
It's kinda one
Like not completely but better than a bunch of terms
i think they both have to be divisible by some power of 2
I have a hint to start
I feel like I've already finished lol
You don't have to explain your process what was your "closed" form for a_i and b_i?
It should have Fibonacci numbers in there
I could see that
sure, I can explain that in a couple ways
you can see it from the binomial theorem when you combine them, the sqrt(5) and -sqrt(5) terms will either cancel or double
$$a_k = \frac{(1+\sqrt{5})^k+(1-\sqrt{5})^k}{2}$$
Merosity
basically my "answer" is just the exponential of the radicals replaced by Fibonacci numbers because they're easier to work with
this is a general trick, for instance you might have seen people do this to get the real part of an imaginary number
here they're replacing sqrt(5) with sqrt(-1), but you're still adding/subtracting conjugates
yeah I've seen that
actually my b_k should have a sqrt(5) in the denominator
to divide that out
so my answer in the end was wrong, but I'm not gonna go through and fix it
This is what I got in terms of Fibonacci I did this really weird method that might not be necessary though $a_n=2^{n-1}(F_n+F_{n-2})$, $b_n=2^{n-1}F_{n-1}$
wait I think tyop
Cube
I see what you mean about fibonacci I've seen something similar before so I can see that working out that's a cool idea
ok worked out some recurrence relations, by taking the kth term and multiplying by (1+sqrt5) to get the k+1 term and collectin gcoefficients, but doesn' tquite line up how I was expecting. But reading your message a bit closer now I'll see if that works
$$a_{k+1}=a_k+5b_k$$
$$b_{k+1}=a_k+b_k$$
Merosity
or rather, I can just diagonalize the matrix now to get the answer
I used vietas formulas to get that
oh?
I collected terms the were on sqrt5 or not on this, if that's what you mean $$(a_k +b_k\sqrt{5})(1+\sqrt{5})=a_{k+1}+b_{k+1}\sqrt{5}$$
Merosity
You can find the quadratic with the root (1+sqrt5)/2 and then do some induction to find a_k and b_k
But I see what you did
Who else doin math counts
sadly i took it for the last time last year
good memories
in mathcounts do you compete infront of a lot of people or is it just a boring classroom environment
like if ur just doing a local school mathcounts
You do it in a school environment
Mathcoutns is fire at the national levels
224 kids
4 kids per table who are on the same team
Environment is great
😭
its a really good question for olympiads so i wanted to share it
probably square both equations and add them to get $2 + 2 \cos(\alpha - \beta) = \frac{6}{9} + \frac{3}{9} = 1 \implies \cos(\alpha - \beta) = -\frac{1}{2}$
higher's secret twin brother
i geneuinly dk
how'd that help you to find cos(a - b/2)
idk
send it here
It’s quite simple 😅😅
dont dm me bruh ask it here
Uhhh ok
So my teacher had shown me a method to generate Pythagorean triplets using 2 other triplets
Using complex numbers
So I thought that I should generalise it
And I have an equation
It would be brilliant if someone could check it
will you provide the solution?
go on
Alright so
Find [2sin(a+b)/ 2]cos (a-b)/2 which is basically sin a+ sin b( its a basic identity you can look up the proof on yt)
And similarly [2cos (a-b)/2]cos (a+b)/2 = cos a+ cos b (eq1)
Divide both the equations then u get tan (a+b)/2
Then just apply tan^2(x)+1=sec^2(x)
With this you find cos (a+b)/2
Substitute in eq1 to find cos (a-b)/2
Simply square it and multiply by 100, boom you solved it
The question is find 100cos^2([a-b]/2)
It's a fun question to solve
Sure shot olympiad question
????? i was exploding my brains out trying to find cos(a-b/2) WHEN IT WAS COS((A-B)/2)???
the request is fucking wrong
how are people so smart lol
hi guys i m back
im the smartest
lol math counts is light work
it's 6-8
but it really shouldn't matter
cuz math counts should rep the smartest schools
I mean the time pressure is the real deal
I bet you couldn't do the questions as fast as the finalists
if you could work on each question for as long as you like then it'd be easy
also yeah they are challenging cause they are extensions of middle school material without going to more difficult stuff
why won't my school let me take both amc 10a and 10b
i thought you could
am i wrong
cause it's your school
but most schools do right
the AMC doesn't care but the AMC isn't the one organising the details of the contest
huh
I'm not sure but at my international school you could only sit it once
they'd choose either the A date or the B date
oh
the mathcounts has really easy questions
a standard 8th grader doing algebra 2 could easily answer every question they give even in national mathcounts
its just you gotta do it fast as hell
fun fact, ... standard 8th graders don't do algebra 2
yeah no
this is just false
its true
its not true
so what level would you AHVE to be as a student to be able to solve these problems without a time limit in your perspective?
there are a lot of problems that require higher level maths to be solved quickly
without a time limit is much different
with time limit you need a lot of knowledge on tricks and stuff
What is the highest “higher level math” that you’re talking about here
i know for sure a standard 8th grader would be scared shitless of this
and this isnt even a nats problem
often times calc is used for some problems
to speed up the process a lot
I mean i would be scared because i AHVE to do it fast but its like a final end of term exam for geometry kind of question
then solve it right now
im eating
mathcounts?
this problem is sus
@soft vigil was this a sprint problem
yeah
p27 of states in 2023-2024 year
oh this
just extend AD
to intersect CB
yeah
buboblakistoni
how would you do this lol
coordinate bash to find B, three points uniqely define a circle, find the center with said three points, use it to figure out radius, pir^2
is the obvious way
there's probably a nice trick
oh yea, just make everything into coordinate geo
valid
not in the spirit of the original quote but yes, coordinate bashing, the devil's marvelous machine
i would just use linalg or something here, i'm sure it works
but that's the obvious soltuon
not even sure I can solve it, granted I don't do comp math, but I'm still a grade 11 honors math student, no way in hell an average 8th grader who hasn't taken geometry is getting that
i have now filled a page with diagrams and am not anywhere nearer solving it
do u know how to get to the center from the three points
i can do it with a lot of trig, but mathcounts is no calculator right
hi please someone can tell me how to prepare for olympiad geometry from basic/intermediate to olympiad level/
Any math helpers dm me
sps a,b,c define a circle, then consider the lines ab and bc. then draw the lines perpendicular to them. the point where those lines intersect is the center of the circle
yea but the obvious solution to that system uses trig
mm ig but can't you just solve for the center directly
like
take the three points you have
then consider the equation for a circle
plug them in to get three equations
with a little bit of manipulation this is a linear system so you can just solve for the center
then boom
you don't need olympiad geometry skills, i almost made it to my national team whilst not solving a single geometry problem along the way!
that's also probably why i almost made the team
wow where are you from
anyway what sort of olympiad level r u talking about? USAMO?
UK
international mathematical olympiad
oh as in r trying to improve ur geometry skills to be good enough at IMO geo?
or like trying to get to IMO?
anyway i can offer some basic advice though:
i like to get in imo team
sir can you please dm me
ah k
Oinks
Ok
Visiting the farm where several dwarves live, Bob organizes 4 forest trips, each of which is attended by all the dwarves on the farm. Each gnome has a red, a white and a black cone. The dwarves use one of their cones on each trip. After examining the colors of the cones used by the dwarves on the trips, Bob notices that no two dwarves use the same color cone on more than one trip. According to this, what is the maximum total number of dwarfs on the farm?
9?
xooks
ook
skibidi
trivel
trivial?
any math helpers?
what does 3-6 and 2-4 mean? is there like a consistent way of ranking olympiad difficulties?
yes, I'll link to the AoPS page
wait they're not using this difficulty scale
on Google
whats the diffrence between competition and olympiads
I don't think there is a difference
why is the intermediate competition split from the others and why is it not called intermediate olympiads?
oh wait on that page
yeah so basically they mean competitions are anything not at Olympiad level
i.e, in the IMO sequence
olympiads test the foundations of IMO level material or are IMO level themselves
yeah there's several difficulty rankings
i suspect that's probably the AOPS ranking
MODS 1-10 is also sometimes used
Evan Chen has also rated like all the olympiad qs in MOHS
competitions are generally easier, u don't need to write proofs etc.
it's complicated by the fact a lot of competitions style themselves as olympiads
Kirkman's schoolgirl problem is a problem in combinatorics proposed by Thomas Penyngton Kirkman in 1850 as Query VI in The Lady's and Gentleman's Diary (pg.48). The problem states:
Fifteen young ladies in a school walk out three abreast for seven days in succession: it is required to arrange them daily so that no two shall walk twice abreast.
specifically this
so you can do 9 dwarves i don't know if it's the largest
Thanks
please do not
please don't advertise unsolicited here.
thanks smay!
100a + 64 and 201a+64 is both squared number Less than 10000 what is a
I try to make it to
A^2-b^2
(A-b)(a+b)
So I could get 101a = (x-b)(x+b)
After that I'm confused
Or did I do something wrong
yeah that's the right idea!
unfortunately the problem ehre is that we still have a
can u do something so that we get rid of the a?
How bout I make x-b is equal to a and make x+b equal to 100
Then I make it into linear equation
why would x-b = a etc. give an answer?
why is the optimal not x-b = 2a or whatever?
Actually this can be solved even with a on the equation, but i'm curious on the way you did it
Try continuing on this and see what you can do
It's just a matter of substitution and sheer will, and you can easily form a quadratic
To quantify diffiiculty level,
https://jaymaron.com/fermi.html
The MIT high school math contest has an algorithm to dynamically decide problem weights based on how many people solved the problem.
Putnam publishes data for problem score distributions so you can judge the difficulty of a given problem. It also publishes the function of total score vs. rank. The above plot is an averaging of this function over many years. Do other contests publish such data?
oh interesting
also i realised my thing isn't as straightforward as i assumed it would be
u can eliminate the a and end up with a pell's equation
pell's equations are quite well-studied so if u end up with that u can just use theory to finish the problem
Is $f:[0,\infty) \to [0,\infty)$ such that
[f(x+y)=f(x)+f(y)]
For all $x,y\in [0,\infty)$ only have $f(x)=cx$ as the solution? If so, what's the proof on it?
Its_TheMathCraft
basically 101a = (x-y)(x+y) where 100a + 64 = x² and 201a + 64 = y²
You only get (101,a) or (101a, 1)
But we use (101,a) cause why not
y+x = 101
y-x = a
y = (101+a)/2
Then x = (101-a)/2
Substituting on one
100a + 64 = ((101-a)/2)^2
400a + 256 = a² - 202a + 10201
a² - 602a + 9945 = 0
(a-17)(a-585)
Obviously a = 17
why are those the only possibilities?
what if you can split a=12 say and it's actually split 101*2 and 6
i agree in that gets a potential solution
but you haven't found all a
actually i suspect this is true
you can probably extend ur original f by setting
g(x) = -f(-x) for x negative
probably can then show g satisfies the F.E.
so f is the +ve side of a cauchy FE solution
and bcus pathological cauchy FE solutions are dense in R^2, we must have f(x) = cx
i haven't properly checked this though
it might not be true
Is it worth doing later AIME problems as practice just for mathematical/ problem solving skills? My country uses BMO1/ 2 which are easier than JMO but are proof based. I think my proof writing skills are fine but is it worth doing those problems just for the sake of improving maths for olympiads?
Learn the A level math and further math pure content, then use AoPS and past papers to prepare. Personally thats what I would do, unfortunately I didn't do it last year out of pure laziness and I missed out on alot of potential I had
not everyone does A levels
He said his country uses BMO1/2 so I assumed he would be following the british spec
oh shit I didn't read, right
further math isn't really related to BMO1/2 though
agreed there's even a huge difference between further and STEP
in terms of format and everything
Some parts of the core pure and further pure spec are useful, also studying pure maths in general just helps problem solving
like even if STEP isn't about proofs, the standard of working is pretty high
they prompt you very little
Are you doing this for STEP prep?
you're supposed to just write a page of working naturally without needing hints
no i'm doing this for bmo1/2 prep
If so then you should definitely do most if not all of normal and further a level maths, then do the STEP prep modules
step prep is adjacent too as well
also trying to understand a level fm concepts a bit more ref:
Then as I said, do pure maths, not all of it is needed obviously, then AoPS is really really helpful (at least it was for me) and just spam past papers
What year are you in?
I see
do you mean the forum or the books?
the books are a bit easy
Which book did you use
ive had a look at all of the official aops ones
Weird, did you do the BMO last year?
yeah
you applying to Oxbridge then lol
yes cambridge
low distinction
i got lucky -- last years paper was very easy compared to other years
and i wasnt very good last year
Quite strange because I found their books quite useful and I also got low distinction on BMO1 and iirc merit on bmo2
vol2?
vol1 was almost fully easy, just that odd thing here and there, vol2 was decent
i'm using mont and art and craft of problem solving by paul zeitz
i need to learn how to do functional equations properly
I was in y11 when I sat the BMO btw so maybe thats the reason
ill get cooked in BMO dont worry i have done 0 prep cause im a lazy mf
i got 120 haha i just made a stupid mistake on the dice question
but bmo qualification is all that matters
anyway for me i just want to get into cambridge over all of that
Bro I actually feel so bad
Getting the dice one wrong is just
wild
Did you not know that the opposite sides add up to 7?
i did the algebra and i went to plug in the solutions so i could see straight away 4 would work so i thought thats the answer
if i had tried 2 i wouldve realised oh right they sum to 7
I guessed the circle area question
a lot of my friends got question two wrong so hahaha
Time to make new friends
I want to sit STEP in y12, I need to do 2.5 chapters a week then go through all the step modules and past papers 😭
both step papers?
Yeah
then just sit it in year 13
Yeah but I want to increase chances and also want to use it to show other UK and US unis
could you help me with my question that i linked?
Let me have a look
I recently started this so I may not be the best person to ask but cant you just plug in x+iy, multiply the numerator and denom by conjugate of the denom then set the real part equal to zero?
Yeah that's what I mean by I can do the algebra but I don't get how they affect it geometrically
Honestly mate, I don't know, my class is starting this content in a couple lessons and my teacher gave me a question so I could get started early and my research from thats all I know
Math, FM, CS, Econ
This is the question $Let ( z_1 = a + bi ) and ( z_2 = c + di ). Determine the locus of ( z_3 = \frac{z_1}{z_2} ) as ( c ) varies.$
Bitwise
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
Oops
you both British btw?
Not British nor live in Britain, just go to a british curriculum school
i'd probably just recommend going
BMO1 -> BMO2/IMO easy -> IMO/ISL
do u have the BMO1 book?
forgot the name of it
cause LY is British so I was just asking, cheers m8
IMO easy is on the level of BMO2??
basically i just worked through all the BMO1 problems from 1996 - current and that worked for me
and then i just started doing problems i enjoyed
the harder end of BMO2 is comparable to IMO medium
The primer? yes i've been working through it
i.e. something like BMO2 2022 Q3 is probably ~IMO medium
(so p2/p5 standard)
i've been doing around 4-6 questions a day
yeah u'd be surprised, IMO easy questions are a lot easier than u mightthink
yh yh fairs
yeah i'd suggest working through the entire book
once ur done with that work through the entire BMO2 book
and that should certainly be enough for camps
what about theory specific i.e mont
So if I got merit in BMO2 what does that mean
mont?
i'm trying to brush up on number theory for itnerviews too
as in like u'll do problems
often with BMO1 questions u can learn the theory bit by bit
@high goblet What was your best placement in BMO2?
but like yeah ofc u'd also want to develop theory alongside
EGMO is a very good book
egmo is a bit hard i've been avoiding geo
(not european girl's maths olympiad lol, euclidean geo book)
i've heard no euclid geo in interviews so like
basically everyone in like trincamp will have a copy
yeah i really dislike geometry too
i can sort of bash around/ just do bmo1 geo anyway without much but for bmo2 i mght use it like post interview
to prep for bmo2
sorry i'll reply to u in a bit lol too many msgs
but like the tactic for if u dislike geometry is basically to learn a bit of synthetic geo
no worries just thought you didnt see
and then once u've learnt enough u can then often bash the end of the problem
NT doesn't really come up on interviews
where r u applying out of interest?
Why trinity?
this chat is so British my water turned into tea
basically NT is quite oly-specific and spec-specific (i.e. we did 0 NT in our school) so any NT you get in interviews will basically be approachable without having to know i.e. FLT etc.
ahaha
hopefully i shall be seeing u next year then!
yeah the interview qs they do are quite olympiad-y
i was going to ask where to find mechanics questions of suitable difficulty?
the question u find online are probably slightly easier than the ones u'll get
Armand from KoreanEnglishman goes to Cambridge
apparently this other guy from Cambridge saw him around campus a few times
yeah i'm not too comfortable with orders/ flt but things like being really good with mod arithmatic is something i'm focusing on
sorry for derailing chat
what do they study?
just don't do mechanics lol
on my test, there were 9 non-mech questions and 1 mechanics question
looked at the mechanics question and went 'nope'
history and politics
so i did all 9 other qs
oh damn they're doing Tripos then
right
unfortunately i don't now the history and politics ppl too well
but as a serious answer, probably just STEP and trinity's sample tests?
also Cambridge is insane for not allowing resits
I heard some really bad things about students who have a medical emergency and the administration has no mercy
to solve diophantine equations as well mainly
easy ones
okay
i've done the sample ones
it's only like 1 or 2
we're not meant to share our interview questions lol
there's this really weird sample question as well let me show you
yep i know
but i can DM u like my rough memory of my interview questions if u want them
sure that'd be nice
i personally don't have any medical issues but i've heard that u should be able to get compromises for medical emergencies?
this second part was weird in explaining it
but yeah unfortunately it is just 1 exam at the end of the year
i don't know if it's really a good question either it's just algebra
(you also get ur ranking in the year so ig only 1 exam means u can have an official ranking)
yeah it's this elite uni culture
ooof didn't know abt that
yeah the rankings are a bit outdated
but if u do well it's kinda nice knowing ur ranking lol
10th/259 :)
for what exam?
remind me roughly what merit is?
cambridge 1st year exams
6+
ah right
the easier questions for BMO2 are comparable to the harder questions for BMO1
but yeah if u want easy IMO easy problems
Yeah, geometry always fucks me over no matter how easy though
oh ahaha it's fine
i suck at geo too
i am doxing myself lol but 20/40 in 2022, 35/40 in 2023
A month until BMO1, I want to qualify for BMO2 this time, should I spam BMO1 papers? Or do something else to prepare
"i suck at geo" gets 35/40
yeah i tried to do as many alphas as possible
i improved at geo in Y13 but in Y12 i really sucked
i did 0 geometry questions in BMO1 and BMO2 in Y12
and then i proceeded to do a further 0 geometry questions in TST1,2,3 and 4
this is interesting, talking about accom
for fun / if you want to make a team / camp
yh true but it's for team
Not british : (
huh interesting
And my country has a different weird system
will u have spent 3 years in the UK educational system?
oh wait no they don't allow non-UK schools
do u hold a british passport?
Nope
The country Im originally from, which I dont happen to live in and they have a weird system with little information online for qualifying for olympiads
sooo yeah
tough
I guess Ill just do some undergrad olympiads
oh yeah it's a bit mean lol but yeah the d/dx are operators
oof unfortunate
it feels like just weird notation over anything else i don;t think it's hard per se
what even is an operator
And olympiads would be very helpful for getting into the job I want to do so it hurts even more : (
which job
have u done this problem?
it surprisingly doesn't require much theory
quant trader or more generally a quant job
and if u do it ur smarter than 1/2 the chinese team and most of the south korean team
like you clearly have the passion and engagement for maths
i have heard many annoyances about this problem haha
it could be something small such as tutoring secondary school students
yeah it's like when you expand, you apply the d/dx
Am I missing something because part i and ii seem easy?
basically they said the interview questions will be about getting you to explain your thinking, like Google or big tech if you know about those
it's easy it's just weird
I see
like explaining bit