#help-36
1 messages · Page 283 of 1
hmm
also, consider that the constant functions are continuous
that tells you something about the cardinality
wait
is it similar
Let $F$ be such a set. Observe there is a bijection $g: \mathbb{R} \to F$, where $g(r) = f_r$, and $f_r : \mathbb{R} \to \mathbb{R}$, where $f_r(a) = r$ for all $a \in \mathbb{R}$. Therefore, $|F| = |\mathbb{R}| = 2^{\aleph_0}$.
toast
that's not a bijection
wdym by thqt
o
there are continuous functions that are not constant
oh
no this is just proving set of constant functions
it is an injection, though
\textbf{(j) ${f: \mathbb{R} \to \mathbb{R} : f$ is constant}.}
toast
ok, you see that (j) is a subset of (k) right?
so the cardinality of (k) is at least the cardinality of (j)
yep
so now i need to figure out the upper bound
yep
do i just need an injection
soemthing like this
if i can show an injection from continuous functions -> real numbers am i good
yes that would do it
then you have injections both ways, so by schroeder-bernstein there exists a bijection
ye
wait
so you said
a continuous function can be uniquely identified by the rational nmbers it takes up?
it's uniquely identified by the rational subset of its domain
if you know f(x) for all rational x, then you know f
simply because for arbitrary y, you can take a sequence x_n of rationals such that x_n -> y, and then by continuity, f(y) = lim f(x_n)
ohh
so we have a set of rational numbers
we want to maybe inject a subset of Q to R
well, it gives you an injection from your set to the set of all real-valued functions on Q
see if you can determine the cardinality of the latter set
that is aleph_0^aleph_0 = 2^{aleph_0}?
what's your reasoning?
well set of all real valued functions on Q seems just like {f : Q -> R}
any function f is in
|R|^|Q|
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What does it mean by 108 are either made of clay or have coloring? Based on my understanding it's saying 108 artifacts are either clay or colored and no between???? Then I look at the 81 and 34 and that doesn't add up to 108
do step by step
that means there's a total of 108 artifacts with either clay or colouring
for example, 60 artifacts have colouring and 48 made of clay
So 115 artifacts they take out 150 and of that 150 we have the 108
That are like either this or that
😭
Huh 😭
You already knew that Clay is 81 and Colouring is 81.
No color and made of clay plus no clay but colored are equal 108
Do you know Union rule?
No
set theory
A U B = A + B - A cap B
A unions B here is 108, as given.
Also knew A and B, then how many artifacts both coloured, and made out of clay?
The table here is perhaps unnecessary in my opinion.
What is a cap b
A intersects B
Oh
Upside down symbol for U
My answer is 7
sorry for interrupting but perhaps OP may have heard of this rule referred to by its proper name, inclusion-exclusion.
7 is the number of the artifacts having both property, you would need the probability of them.
Thank you for your explanation, I used Union rule term in my country 
Correct.
Congrats!
fahhh
!done
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Is my proof correct? \noindent \textbf{Problem.} Prove that $\frac{1}{n+1} < \log(n+1) - \log n < \frac{1}{n}$.
\begin{proof}
Note that
[
\log(n+1) - \log(n) = \log\left(1 + \frac{1}{n}\right) = \int_1^{1+\frac{1}{n}} \frac{dx}{x}.
]
Now, for all $x \in \left(1, 1 + \frac{1}{n}\right)$, it holds that
[
\frac{n}{n+1} = \frac{1}{1 + \frac{1}{n}} < \frac{1}{x} < 1.
]
Therefore, due to the continuity of $\frac{1}{x}$ on the interval $\left[1, 1 + \frac{1}{n}\right]$, and by Theorem 13-7, we have:
[
\int_1^{1+\frac{1}{n}} \frac{n}{n+1} , dx < \int_1^{1+\frac{1}{n}} \frac{dx}{x} < \int_1^{1+\frac{1}{n}} 1 , dx.
]
Evaluating the integrals of the constants:
[
\left[ \frac{n}{n+1} \cdot x \right]_1^{1+\frac{1}{n}} < \log\left(1 + \frac{1}{n}\right) < [x]_1^{1+\frac{1}{n}}.
]
This simplifies to:
[
\frac{n}{n+1} \left( 1 + \frac{1}{n} - 1 \right) < \log\left(1 + \frac{1}{n}\right) < \left( 1 + \frac{1}{n} - 1 \right),
]
[
\frac{n}{n+1} \cdot \frac{1}{n} < \log\left(1 + \frac{1}{n}\right) < \frac{1}{n},
]
which yields
[
\frac{1}{n+1} < \log\left(1 + \frac{1}{n}\right) < \frac{1}{n}.
]
This completes the proof.
\end{proof}
YuyuHenry
This is the theorem I'm citing
Seems legit
You can also prove it without srtting up an integral by means of the mean value theorem
But like, it's without strict inequalities
so the thing is that I don't know if my cite here is correct, I need it with the strict inequalities
really?
Yeah i guess you need to modify your logic slightly
U can still use it
But like
f(x) = 1/x is strictly decreasing and constant on [1, 1 + 1/n] which means the bounds are not reached and ur inequality is strict
you could try to prove that if f is continuous and if there's some point in [a,b] where it's strictly between m and M, then the inequalities are strict
yea, that's what you want basically
Its like a four liner woth mvt yea
can I see it?
Its in my head and I dont want to latex rn sorry
okay, so let me try
by MVT of $\log x$ on $[n,n+1]$ there exists $c \in (n,n+1)$ such that $\frac{\log{n}-\log{n+1}}{1}=1/c \Rightarrow \log{n+1}-\log{n}=-1/c$, and we have that $\frac{1}{n+1}<- \frac{1}{c} < \frac{1}{n}$ we're done
YuyuHenry
@rugged merlin like this?
U got rhe right idea
But you messed up ur signs
It should be log(n+1) - logn
sorry to interrupt but wouldn't you get in a little bit of nitpick trouble for applying the MVT the wrong way in the first place?
I forgot the signs lol
But ur denominator is not right then
Elaborate
never mind, I was just thinking that even though OP multed by -1 to 'fix' the signs, the application might be wrong to begin with so some pedantic examiner could dock him for misuse of the MVT.
maybe it's not a concern though, sorry for interrupting.
This is what i was pointing out yes
ah, sorry for interrupting once again then.
I mean bt that logic -1/c would be a negative number which would be apparently sandwiched by two positive fractions
Which doesn't make a whole lot of sense
ohhh I see
You're good 
(though if I may comment, please bracket the n+1 in the log, so as not to confuse it with log(n) + 1 when reading back later!)
thanks
by MVT of $\log x$ on $[n,n+1]$ there exists $c \in (n,n+1)$ such that $\frac{\log{(n+1)}-\log{(n)}}{1}=1/c \Rightarrow$, and we have that $\frac{1}{n+1}< \frac{1}{c} < \frac{1}{n}$ we're done
YuyuHenry
From what im understanding you are building up yhe theory on integrals from the ground up, so you are likely formally defining the logarithm by its integral form
yes
Probably if I write the MVT my teacher will say "didn't I teach y'all how to integrate"?
The fact thst the derivative of logx is 1/x is proven later so you probably cant (shouldn't) utilise that uet
not to mention, if I may comment again, isn't that Spivak's Calculus?
U got it now
we're in sequences
so we're already past that
But did you prove FTC
If I apply the MVT for derivatives on log(x) to solve an integral problem before the FTC is established, I am using circular logic and relying on maths that I dont have access to yet
Oh ok
are you in chapter 18?
22
almost done with the book
"almost"
This is supposed to be introductory calculus
in that case, just for context for Lex, OP probably has access to many theorems.
Upload your suggestions for when maths 2.0 drops
Ofc
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hello can someone explain how you approach these kind of problems
did bro sleep 💀
Which one
I WILL FAIL MATH TOMORROW
the 2.1
anyone here know k map?
For the first one you have 6 total and your goal is P(RRG)+P(RGR)+P(GRR)+P(RRR)
Like when you pull 3 times you want at least 2
But i mean how do you differ between a green and red gummy
or is that not necessary
You nees to compute the current probability
First try red is what
Also let's do P(RRG)
Oh well you did Gegenwahrscheinlichkeit
1-P(RGG)-P(GRG)-P(GGR)
Hmm doesnt seem better
no there are only 2 green gummies tho
Oh right
Ok one less probability
So first try red is 4/6
Then twice green is 2/5 * 1/4
So P(RGG)=4/6 × 2/5 × 1/4
so 1-P(GGR)-P(GRG)-P(RGG)
Yea
but why do i have to consier
the order
is that important too
like green first then red
What do u first want in 2
n?
wdym
hmmm
id say some stuff like
2 * something with n but
we dont even know
n-1 also
but in the denominator too?
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i need help
so im learning the vector cross product
a x b = magnitude of a x b x sin(x) x n
i understand when i do a cross b i get a vector,
what is that vector?
is it n?
what does the rest of the formulae mean
that is an orthogonal unit vector
yeah it is n,
Or unit normal vector
a what now
with magnitue the same as absinx
It is a vector that orthogonal to the plane containing both a and b
so n = absinx
magnitude
i have no idea what orthogonal means
perpendicular
Perpendicular
perpendicular to a and b. with a caveat
idk what caveat means either
u have to follow the right hand rule
u have to follow the right hand rule for direction
i just mean it needs some nuance
because there are two vectors perpendicular to a,b
like it can point up or down (will be perpendicular either way)
that just gives u how long the vector is
it just so happens to be the same as the area of parallelogram a,b forms
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so here right
Pf!(Z
aber Z! ist doch das es fair ist
was die wahrscheinlichkeit fuer fair ist
nein
Z hat nichts mit fair zutun
oh
ha warte
doch
Z ist, dass es gezingt eingestuft sei
also das ist sicher nicht richtig
Nicht dass es IN WAHRHEIT schon so ist
genau
hä also
.
oder besser gesagt
er wurde bereits als gezinkt eingestuft
nun willst du wissen, mit welcher wahrscheinlichkeit dieser gezinkte wuerfel fair ist
denn gezinkt eingetuft heisst nicht immer unfair
Du willst die Wahrsch. dass es eigentlich fair ist, in Anbetracht dessen, dass es so klassifiziert ist
ein zufällig herausgegriffener würfel, der als gezinkt eingestuft wird, fair ist
das heist doch einfach, Die wahrscheinlichkeit von einem fairen würfel unter der bedingung das es gezinkt ist
ja
genau
.
aber
ngl ich kenne diese Notation nicht
ur not german right
wtf
yes in germany we use different notation for conditional probability
bro speaks better german than me
we dont use P( A | B)
ye
We use P_B (A)
Ich verstehe aber was gemeint wird, 'so es ist mir problemlos
hab in der Schule gelernt
ich hab die aufgabe falsch verstanden
Ist ein bisschen besonders ausgeschriebn
keine Sorge
Wenns "eingestuft" vermisst wird, ändert sich das Problem
aber doch jetzt einverstanden, wie mans löst?
Ich überlege gerade
ja aber die aufgabenstellung ist sehr komisch irgendwie
Der Würfel "sei" gezinkt, dh wir sind mit einem "Z" beim... Baumdiagramm?
-# nennt man es so?
Davon ausgegangen, dass wir also ein Z haben, was wird die Wahrscheinlichkeit sein, dass wir auch ein F (fair) haben?
-# hier kommt Star mich zu korrigieren 
ja
Ops sorry bruh, P(orange)=1-P(nicht orange)=1-n/(n+1) × (n-1)/(n-2)
cool
also ist es dir klar warum wir das berechnen wollen
Hallo Schildkröte und Wlan
hallihallo
i basically thought, that Z! means not gezinkt which means fair
WLAN was zum 
but yeah, Z ist "gezinkt klassifiziert", nicht "gezinkt in der Tat"
oh so the dice should be Fair, but classified as gezinkt
yes
genau
oh i have 60 minutes for 24
and no calculator allowed
is bro at harvard or some shit 😭
man theres just so much content that could appear
ich meine, braucht man honestly nen Taschenrechner?
honestly i must neglect some stuff snd gamble
Use fractions and make your life a little simpler
First, what's the probability that it's classified as loaded?
(fok I was gonna acc write "klassified as zinked"
)
Wait so P(F and G)/P(F)
ja
yeah
ja der nenner ist falsch
oh then P(Z)
on the bottom, yeah
yeah
sorry that's just funny to read lmao

Weil's fast alles schon auf Englisch war, hab ichs mit nem englischen Akzent lesen müssen 
okay so 1.1 i could just say that for value bigger than 3 there is a negative root which isnt possible right
smaller than -3 and bigger than 3
but
Outside of the range, x^2 > 9
if i were to insert -4
THIS makes the square root contain a negative inside it, which is not solvable
then you get sqrt (-7)
wait i never properly understood
it is solveable
-3^2 is -3*-3 which is 9, but isnt (-3)*(-3) the same basically
Currently translating dw
so when is () making a difference when using potences
-3^2 is just -1 * 3^2 = -9
Translation into English:
- Given is the function f with f(x) = sqrt( 9 - x^2 ). The graph of the function f is a semicircle.
1.1. Explain why f is only defined for x in [-3,3].
1.2. The graph of f is rotated in the interval [-3,3] around the x-axis. Evaluate the volume of the body of revolution, and describe its shape.
and (-3)^2 = (-3) * (-3) = 9
but -3*-3 is also 9
yeah thats what i said here
yes, but when you say "x ^2", you mean "take whatever x is and multiply it by itself". So if x = -4, say, then the minus is counted INSIDE the bracketed expression
That is, if x = -4, then x^2 = (-4)^2 (because I take -4 and multiply it by itself) - so this evaluates as 16
Is tmrw exam
man you see the 1.2 this is what im talking about
,w x = -4, calculate x^2
yes
Ts u do in one semester lwk
I mean, it's a spun semicircle around the x-axis along that interval
What shape does it take, first?
man im boutta restart this year 😭
(that might help you find the volume more easily)
But yeah u have other subjects too 
i mean
a semi circleV
we learnd how to do this stuff before i just gotta relarn it
man i dont know how you guys just immediately know how to solve stuff directly even when ur probaly not doing this in uni or whatever
Try spinning a circle instead
I'm assuming they mean spinning a circle on its center
kind of like making a coin 180 on itself
https://www.geogebra.org/m/RyGPhBtU#material/NPpFNnWA has a good animation of this btw
I thought ur finals was today damn
I alr took mine and was cooked
tomorrow
ne Kugel?
-# damn, study well dawg I was all confident and shi saying my country's education ain't shi I was wrong
i still gotta go through hypothesis tests, some plane vector stuff and some probability
yeah like a sphere
but i mean
it said semi circle
does that still make it a sphere
yes right
because it spins like that
yeah
ye
because it's gonna double around itself
Right, so we've got a sphere with... what as its radius?
weneed to intrgrate something ive done this before but i forgot
shit like
1/2 pi *
some stuff like tha
yo theres no way i gotta memorize this hell nah
(4/3) pi r^3
damn
oh you can do this by integration yh
hold up lemme see if I can get a textbook screenshot of that
(wird aber auf Englisch)
let me check my notes
soll irgendwo da sein, yh
Gefunden
[Source: Edexcel AS and A Level Further Mathematics Core Pure 1/AS textbook, page 72]
If nothing else, the blue box
yeah
See also: Doctor Who
i swear bro 😭
oh there's a timelord below this channel anyways lol
they show the herleitung
yeah
but for 99% of the students its too difficult to understand
and everyone only reads the blue box
The idea is that, when you're not rushing to learn the content, this is supposed to motivate the definition
we had to do the background of integrating once
When you're pressed for time, that blue box gets you quite a good way there though
yeah us too i think
ill probably open a help chanel some time later when im stuck on something again ty
.close
yo ure welcome
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My theory, i want ur thoughts
📜 THE SIMPLICITY IMAGINARY STANDARD (V1.0)
A Simplified 2D Simulation Logic
🧭 1. THE COMPASS
- Standard: I = 90^\circ
- Anchor: 360^\circ (Top/North) is the Origin.
- Rotation: Always Clockwise.
- I = Right | 2I = Bottom | 3I = Left | 4I = Reset Top.
🚫 2. THE GOLDEN LAW
- Linear Only: Use Addition/Subtraction for movement.
- FORBIDDEN: SQUARING (I^2) IS ILLEGAL. * Logic: Prevents simulation crashes and keeps calculation speeds maxed out.
🔍 3. THE ZOOM & SNAP
- Micro-steps: 1I contains 90 sub-units (degrees).
- The Snap: Round complex decimals (e.g., 45.123) to the nearest 0.1 for efficiency.
🌊 4. THE \pi LINK (Curve Distance)
- Formula: \text{Dist} = (\text{Turns} / 360) \times (2\pi r)
- (Lazy Mode: \pi = 3)
Purpose: Designed for high-speed game logic and "Lazy" physics engines. EPIK. Logic > Complex Trig.
This used ai, but the idea came from me. Ai is built to help and assist human. So i used it to assist me
So... What do you want to ask?
!noai
Please do not trust ChatGPT or similar AI tools for mathematical tasks, as they often generate output which "sounds correct" but has numerous factual or logical errors. Use of these AI tools to answer other people's help questions is strictly against server rules (see #rules).
you seem to have merely described a bearing system. what's your question with it?
Is that factoid necessary?
if you're looking for opinions it might be better to ask in #math-discussion.
help channels are for problems and/or questions that you need help with
It is prolly
#study-discussion perhaps?
Ehh no
Since it is academic suggestion.
Oh
.close
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\textit{Task 22.}
\textit{A triangle $ABC$ is given, in which $|AB| = 6$, $|AC| = 4$, and $\angle CAB = 60^\circ$ (see the diagram).}
\textit{Task 22.2 (0--1)}
\textit{Complete the sentence. Choose the correct answer from the options below.}
\textit{The length of side $BC$ of triangle $ABC$ is equal to:}
\textit{A. $\sqrt{28}$ \quad B. $\sqrt{40}$ \quad C. $8$ \quad D. $\sqrt{76}$}
Addison Tarna
What's this lang
Don't just drop your question here, expect people to solve and leave, OP.
Ya
you need to find bc
Can you stop?
then use it
With the attitude
this is just a reminder that we are here to help you and not give you the answer
b/sin(B) = a/sin(A) = c/sin(C)?
Stop whining
It is your attitude, you dropped it here, not asking for help, or showing your work.
@viscid stirrup
please dont be rude
Mhm and it works here?
Area = 1/2 * a * b * sin(a)?
So it’s this?
@viscid stirrup
But you said it also works
@sonic cairn Has your question been resolved?
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Consider the unit circle $C$ defined in the real plane $R^2$ as:
$\C={(x,y)\in R^2 : x^2+y^2=1}
\Let $T_\theta$ be a rotation of this circle in the counter-clockwise (positive) direction by an angle $\theta > 0$. It is given that $\theta$ is not a rational multiple of $\pi$ i.e. $\theta \notin \pi Q$
Let $M (1,0)$ be a point on this circle.
- Prove that $T_\theta^k(M) \neq M$ for all $k \in Z^*$
- Use the Principle of Mathematical Induction on $n\in N$ to prove the following statement:
For every $n\in N$ there exists an integer $m\in N$ such that the length of the arc of the circle extending between $M$ and $T_\theta^m(M)$ does not exceed $\frac{\theta}{2^n}$ - Prove that any segment (arc) of the circle $l$ o matter how small, will contain an infinite number of points from the orbit $l$, where:
$l={T_\theta^n(M),n\in N}$
$\pi&
4th line of text
Oh yea, and {} is usually problematic.
If you want to make sure it renders properly, \{ \}
Amer
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
Consider the unit circle $C$ defined in the real plane $R^2$ as:
$$C=\{(x,y)\in R^2 : x^2+y^2=1\}$$
Let $T_\theta$ be a rotation of this circle in the counter-clockwise (positive) direction by an angle $\theta > 0$. It is given that $\theta$ is not a rational multiple of $\pi$ i.e. $\theta \notin \pi Q$\par
Let $M (1,0)$ be a point on this circle.
- Prove that $T_\theta^k(M) \neq M$ for all $k \in Z^*$\par
- Use the Principle of Mathematical Induction on $n\in N$ to prove the following statement:
For every $n\in N$ there exists an integer $m\in N$ such that the length of the arc of the circle extending between $M$ and $T_\theta^m(M)$ does not exceed $\theta\over2^n$\par
- Prove that any segment (arc) of the circle $l$ no matter how small, will contain an infinite number of points from the orbit $l$, where:
$$l=\{T_\theta^n(M),n\in N\}$$
youre missing the $ on the end of the C ={...} part.
lol
Anyways, to the problem
I assume Z* is the integers?
Well, the "infinite" part has to do with the fact that the intersection is not just the end points meeting.
And this is somewhat equivalent to proving that, for the rotation T, with theta being a non-rational multiple of pi (that is, in some sense, theta and pi are linearly independent for n in N rotations)
Which in simpler words means that, for an arbitrary amount of rotations for an angle that is not a rational multiple of Pi, you will cover the whole circle once again.
my works is:
let $\varepsilon > 0$ be the length of any given $C'$ of the circle
\for any given $n$ we find $m\in N$ whereas the length between $M , T_\theta^m(M) > \frac{\theta}{2^N}$
Amer
let $\alpha = dist(M , T_\theta^m(M))<=\frac{\theta}{2^n}$
Amer
\leq for less or equal btw
$\alpha < {\theta\over2^n} < \varepsilon$
\over overarches the whole expression, use {} to enclose it
Amer
Amer
yes?
this proves the points are infinite?
I was more of going on this line of thought
lemme try to put it better
With T a positively oriented rotation by θ ≠ πq, q ∈ ℚ, and L (arc) a continuous subset of our unit circumference C; We want to prove that the set ∪_N T^i(L) = C
Aka, from our arc L, by applying T an arbitrary amount of times, and joining all the resulting arcs L', we get back our original circumference C.
If this is true, then obviously, our original L has to have an intersection with this new "reconstruction of the circle".
∪_N should be read as
$\bigcup_{i=1}^\infty$
@sour copper Has your question been resolved?
We know that theta can be written as a θ = xπ with x being part of the irrationals.
As such, we can divide 2π and θ both by π and get 2 and x ∈ R\Q
Equivalently, our rotations now become addition under mod 2.
Soo, we want to know that an interval of the form { ([0,a] + nx) mod 2, n ∈ N, x ∈ R\Q} = [0,2]
I hope youre following with the idea
a here is alpha right?
not really, just some arbitrary real number less than 2
ig i should have clarified
Well, ig we can start to play with what x is in relation to a too
if x < a, then we know that [x,a+x] (aka n=1) will have an obvious intersection with [0,a]
(same idea repeats for every single rotation, and since they all are in an intersection with eachother, then they will eventually fill in the circumference)
if x = a, then we know that [x, a+x] will share an endpoint with the previous interval, and as so, once a+nx > 2 for some n ∈ N, then in mod 2 the interval will have an intersection with [0,a]
So they basically tile one after the other until the last one.
and with x > a we have to deal with the fact that x and 2 are linearly independent w/ respect to natural scalars.
i am type of guy who loves solving by equitation and numbers
but i think this part is more on the talky side
i am drawing blank on how to write it down
ig, we are exhausting options
oh, and just now i noticed, the x < a and x = a can be condensed into one single step.
aka x ≤ a
Okay, i assume i never mentioned why this makes sense, but basically we are redefining our problem in the (r,θ) space instead of (x,y)
Where a "continuous subset" of the circumference is much more obvious.
each segment from M to $T_\theta ^m (M)$ is smaller than ${\theta\over 2^n}$
Amer
i'm having an english moment
Just ensures you that theres some m such that dist(M,T^m(M)) < theta/2^n
For any arbitrary n
but basically if we make C smaller than that, it's guaranteed that some point will fall in C
The problem doesnt revolve around the fact if the arc falls in C
Since by definition its part of C
The problem is asking if the "orbit" of said arc will ever intersect the original one.
if we prove L is dense then that solves it right
Because we havent proven that the orbit is itself the whole C
Ohhhh, yea, i got what you were trying to do previously, the problem is showing that this rotation is positively oriented w/ respect of the original arc position.
my principle is each step is smaller than our segment
Yea, thats the problem, thats not needed at all
Like, the rotation could be near half a circle
while the segment be tiny.
The proof of part b) tells you that after some amount of rotations you will eventually get to a rotation thats in magnitude smaller than the length of the arc.
But not its direction
it will be bigger than the rotation if $n$ in $\theta/2^n$ is big enough
Amer
i suppose
oh.. that makes sense
...
i am having too much info rn i am scrolling up so often
Thats kind of why trying to show that the orbit of L is in reality the whole circumference.
Since at that points its obvious that there must be some intersection
Oh, yea, I found a neat way to tie both ideas. @sour copper
Okay ill try to have it all as short as possible.
First of all, and for the sake of my sanity, i will have this be expressed again in terms of angles and not precisely as subsets of R^2
We have from your work on b) that, for some T^m(M), the difference in angle between M and T^m(M) (which we think of as a length of the arc)
Must be lower than θ/2^n
for any arbitrary n we may choose.
Notice, since θ/2^n is quite obviously lower than θ, we can extend this inequality as α < θ
where α is again this difference in angle.
Now, if θ itself represent a shorter arc than the arc we choose as "L"
Then we follow the x ≤ a i previously mentioned
Aka the rotations T by themselves will start to reconform the whole circumference.
Now, if x > a, we redefine with the idea of T^m, T^2m, T^km... you previously mentioned, as some form of "composite rotations", that, either positively or negatively will reconform the whole circumference again.
You can say that you create a new T' which rotates the arc by α instead of θ
Which ties back to the x ≤ a logic.
Btw, for the sake of writing this algebraically, try to deal with the length of L as an angle itself.
okay
oh btw i omitted a part during translation, r = 1
don't think it's relevant
i think it's obvious
It said unit circle yea
the other way around
my work not looking too good
so after we play with x, i can conclude that
i create $T'_\alpha ^m$
Amer
Compile Error! Click the
reaction for more information.
(You may edit your message to recompile.)
You can avoid the ' notation if you clarify that alpha is just lesser than theta
And the m should be reserved for T_theta
Youd have T_theta^m = T_alpha
we can say that right
Its not precisely the distance, but yea
Not really
If we say that θ ≠ πq, q in Q
Then we can say that θ = πx, x in R\Q
Aka its an irrational multiple of pi.
And by dividing by pi, we just get x, an irrational number.
i am not that good in math i am not sure how theta = xpi transaltes to 2 and then [0,a]
The full circle is 2pi
thats where the 2 comes from.
Is just measurements in radians
[0,a] is the "length" of our arc measured by radians.
consider that a isnt alpha, its just some arbitrary measurement
if you assume that x is the irrational multiple that gives place to theta
Then + nx is just the arithmetic representation of applying the rotation T "n" times
if youre more comfortable with it, you can keep in the π for all the operations.
so theta = xpi + 2pi is not incorrect
nope
Well, its geometrically equivalent inside the circle
but id just keep it as xpi
after we say
we need to elaborate on x whether it be >=a or <a
i got a little confused
or do we say T_\alpha^m = T_\theta
Im a bit occupied rn, but my overarching idea was to show that the "orbit of L" = C, as sets of points.
For that, we start from the definition of C itself.
C = { (x,y) ∈ R^2 : x^2 + y^2 = 1 }, which can be rewriten as:
C = { (r,θ) ∈ R^2 : r = 1, θ ∈ [0,2π) } (polar coordinates)
In this frame of reference, we can ignore the radius r and focus on the angles.
We have that an arc L is a subset L = { (r,θ) ∈ C : θ ∈ [0,πa] }, a ∈ R
So the angle that the arc L has goes from = 0, to = πa, measured in radians
With some rotation T / T_w, were w = xπ, x ∈ R\Q we have that
The "orbit of L" can be defined as the union of all the "rotated arcs"
"orbit" = U_N T^i(L) = { (r,θ) ∈ C : θ ∈ [0,πa] + wn, n ∈ N}
Consider that what we used to call "theta" i just wrote as w, since it would conflict with the notation
You can keep it as theta anyways
And we want to show that this union of rotated arcs is in reality equal to the whole circumference.
For that, we divide into two cases.
-
w ≤ πa: Where its easy to show that one single rotation byT_wgenerates an arc with an intersection with the previous one, so they reconstruct the whole circumference without any extra consideration. -
w > πa: Where you use the conclussion from b) to create a new "composite rotation"T' / T_α, which is what you originally proposed. We have that with some[T_w]^myou get a lower angle than that of the original rotation by "w", so you create[T_w]^m = T_α
This is why i previously divided by π, you can see it appears for all angles.
And from the use of these smaller rotations T_α, you can apply logic as the case 1.
The idea is that from doing multiple rotations with angle theta/w, you can get a smaller "composite" rotation with angle alpha.
brain not in service
lmao.
i need a LOT of time to process that
is there any simpler method by any means?
can i suppose L is a subgroub of C without showing a proof?
or is there something i am missing
L is a subset of C by definition
the orbit of L also is, but we want to show that in reality it eventually becomes the entirety of C
Which ensures that the orbit of L intersects L itself.
just to be sure you follow, i want to make clear that
L, C, and the orbit of L are 3 "entirely different" objects.
More precisely, if you move L by a certain angle theta/w, you get a new arc, which we will call L'
The collection of all L' (depending on that angle theta/w) is the orbit of L
you're giving me all the info i need i just need a LOT of time to get everything as a single solution
We are interested in showing that for irrational multiples of pi, the orbit of L is equal to the entire circumference
which we do with not equations, right?
i am like, really confused how
do i put it down on a piece of paper
like everything here makes sense but if i wanna type it out i go fully blank
we let there be C' an arc >0 -> 'a' is mod 2 theta -> theta = xpi
You can write it down algebraically, yea
Yea, C' or L
We use mod 2 or mod 2pi (depends if you wanna keep in the pi for radians), since angles that go over 2pi can be reduced to a smaller angle.
like, 380º = 20º for us.
3pi = pi, etc...
have we assigned a name to the decreasing arc between T(M) and M
Not really, its just some arc. Doesnt really matter, since we only care for the new angle it creates
btw, if you wanna see how this idea operates, https://www.desmos.com/calculator/wvsgwjgmkr
Its just a way to visualize the concept.
If you set it up for n = 1, w = 0.7, you can see how the first arc rotation deviates to about a third of a circle.
Now, if you dont change w, you make it n = 3, you can see the third arc rotation (L3), is actually just a smaller rotation from the original arc.
On that logic, once you can construct any angle that is shorter than that of the original arc L, you can then cover the whole circumference.
rn i have to study for a chem exam, DM me if you want, once i have more time ill try to write it out if you didnt manage to do it by then.
But i assume that the idea should be pretty clear as of now, its just being able to write it down algebraically.
i will try as hard as i can to word it, but i am likely to fail and dm you 😭
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how do i derivate this?
i keep failing
you mean as in take derivative right?
oh ok yeah so u just use the product rule
(fg)' = f'g + fg'
so take each derivative separately and then just combine em
oh wait i might got it
i think it should be f'(x) = (2x-2)e^{-x} - (x^2 - 2x + 1)e^{-x} if im not mistaken
np
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Hi everyone
Hello Amy
Can we be of assistance?
@smoky night Has your question been resolved?
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no clie how to even start on this
@keen hare Has your question been resolved?
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Ah sorry for the late reply, I see that makes sense yes. Since if $f$ is continuous on a compact set $E$ then $f(E)$ is compact, (so closed and bounded) and hence it attains its minimum and maximum on it, say the maximum is $c$. And then like you say later, since $B(0, r) \subseteq \overline{B(0, r)}$, so then we know the supremum must be $\leq c$ and since $B(0, r)$ is non empty the supremum exists.
LXDL
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please ask your question.
Hi
So if we have a formal system
Can we prove that it can't have self referential statements
isn't it the opposite
?
you cannot prevent it from having self-referential statements
that's what Gödel's whole thing was about
nvm
Yea it only specifically talks of strong systems
yeah welp
dibya's a funny name lol

thank YOU buddha

@halcyon night Has your question been resolved?
What I understand so far is that if a system is incomplete it has to be undecidable but inverse isn't true 
So in this case the undecidable language is the set of all theorems expressible in the system

So like I know how to prove a system is decidable
I know how to prove it's incomplete(this would prove undecidability)
But how to prove it's complete but undecidable



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can anyone help me with these two questions and explain
!nosols
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
Just calculate the value of:
50% of 120 litres
What does 50% mean?
im pretty sure thats what the question is, yea
well done for reading it out
Calculating the value of "50% of 120 litres" is easier than answering the question
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np

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unfortunately nothing...
i didnt understand where i can begin
um thats what we have to find
Seems like the question is worded poorly
It is just trying to find the functions such that f(1) + f(2) = f(3)
yeah
Yeah I just saw the equal sign.
Just go through like each possible value of f(3) and see the possible sums you can have
There is a pattern to be found
i didnt understand
Well f(4) is free to be anything.
And f(3) is determined by f(1) and f(2).
really sorry
If f(3) = 2, how many (f(1), f(2)) pairs do you have that satisfy the equality
so something like this?
Yuh so
Count all of them up
How many in total
15
Now back to the first point here
for f(4) = 1, you have 15 pairs
For f(4) = 2, you have 15 pairs
For ....
How many pairs does it imply in total
15 * 6
Congrats; you're done
90
ohh
btw
i thought of this
if i do something like this
will i get the solution
or did i mess smth up
I dont really understand whats going on in that image I'll be honest
nvm
well ignore the first 1
but what i tried is
in this i took f(3) as 3
and the values in circles are the possible numbers
it can be
but i blundered
f(1) and f(2)
yeah it worked too
tysm for the help
ill close this now
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✅ Original question: #help-36 message
Combi?
Leme trynthis1
i mean i can do smth like this but theres a condition
Size means no. Of s_n right?
!nosols as a gentle reminder, in case you're going to provide the whole answer
As a helper, please do not give out answers that could be copied as a homework solution. Have the student work through the problem themselves and guide them along the way.
wym
No nothin i got it
ight
I understood the ques
I don't think so
We can say s_3, s_4, ...., s_9 can in any of the teams.
yeah
Les leave s_2 and s_1 for now
and what to do with the other 7
Then we will have 7•6 = 42 ways to make X team.
yes
wsup dawg
Fine
ah
no that was the old 1
.


