#help-49
1 messages · Page 109 of 1
oka that was a good one
you got big nostrils
☠️
whats r6
6th wait
bro feels pain
painful fr
I thought maths would’ve numbed it but apparently not
wait actually
don’t put bacc down like that
wow
how did you get
stop pointing fingers at me
the area in the first place
hm
he’s just a human, we all make mistakes
HAHAHAHAHAHAHA
(60⋅2)+(90⋅2)+(110⋅2)+(120⋅2)
ok I see
localbassman can have it
I am kinda confused
how are you supposed to do this using subintervals
probably multiply by 2 to get normal intervals
uhh
(R(0)+R(2)+R(5)+R(7)+R(8)) * (8-0)/2
💀
this doesn't make sense
theres no way
yes
so maybe that's the compensation
ahh so e^iπ in this sense goes to 0 as the derivative of x^2 is 2x and plug in y
I get it I get it
draw
eh
no
hm
maybe ask teacher and or professor
idk what that erf is i dont rlly get how he integrated that
that seems right ngl
erf
never seen in my life
errorfunction
WHAT
like the planet we live on?
anyway irrelvant
LMAO
oh what
so thats wrong
it does
it does until i see erf
(Idk what ur doing I’m just being supportive)
,calc (0+2+5+7+8)/4
Result:
5.5
ok I think i know
good luck guys !!!!
okay
so we need to rewind first to a and b...
we wanna have 4 itnervals
mhm
meaning 4 rectangles
yes
how many rectangles in a square
actually it's simpler than thought
hm
Delta_X = just the difference of x_i and x_j
uh yes
Yes
So we sum up
integration
R(0) x (2-0) + R(2) x (5-2) + R(5) x (7-5) + R(7) x (8-7)
never mind then
l*b?
60 x 2 + 90 x 3 + 110 x 2 + 120 x 1
,calc 60 * 2 + 90 * 3 + 110 * 2 + 120 * 1
Result:
730
730
not 760
yup
yup didnt seem any other way around that
did u figure it out guys
,w 100 + Sum[2 * 400e^((-(2k)^2)/4), {k, 0,3}] - 730
uh mayb
For The approximated integral of D(t) we used 4 subintervals but used Delta_t = (8-0)/4 = 2
A consistent Delta_t instead of having a new width everytime
real real
okay and the width is 2 is that the change in t
and left point rule, not to forget
what
delta t
ok nvm yuh
yuh
yuh yuh go on
Ok I would go with that
well done
what about r3
no leave r3
but r3 is cool beans :((
undefined
bacc (unhelpful)
yup
so its just that
it's not deep but i am fried today
am i deadass getting 6 marks for writing tis though
from me yes
why does it have such a high mark allocation
The fact that your friend used erf(u) is so funny
hes such a bozo
that made no sense Lmao
cleanliness is next to godliness
derivative
average derivative
oh wow ur already ahead
haha
bacc is super helpful
real
such liars
and what about my emotional support
true
u were the brain
i was both sides of the brain :D
the heart
so real
such kind words
😂
@shadow scaffold
okay can i bother you again later when i study in an hour or 2
i will take a break now
just open a help channel
and second you're supposed to message the bot lmfao
okay bet
bro you are really lost ngl
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Anyone know how to calculate newton polynomials?
Please don't occupy multiple help channels.
Sorry i don;t see my topic
close one of your channels
when i close one i close two
i don't see this channel
i literally just sent you a link to that channel
Can guys close this channel 32 because i dont see
ok thanks
Go to "channels and roles" at the top of the channel list, you may be hiding the channels
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hey I'm quite lost here and would appreciate some help
with L being the angular momentum operator, fulfilling $[L_j,L_k] = i \varepsilon_{jkl} L_l$
tobi
should I look at each matrix entry?, I just dont see how these are equal to one another if i write down the taylor series
already found a way of solving this
.close
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for this example how would you draw the graph?
Im trying to draw it but there seems to be an additional tri edge {a, s, c} but its not in the set of tri edges
@real pivot Has your question been resolved?
@real pivot Has your question been resolved?
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hi
i just want to confirm that my approach is correct for this question
what i have:
$$F_U(u) = P(min(X,Y) \leq u) = 1-P(X>u, Y>u)$$
(taking the complement above)
$$= 1 - \int^{\infty}_u \int^{\infty}_u ye^{-(x+1)y}dxdy$$
jack
and then solve by fubini? hpoefully this looks fine
Yeah seems good to me
thanks 
looks good
@dense bay Has your question been resolved?
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Let $a>b$, then by the mean value theorm there exists $c \in (a,b)$ such that $f'(c) =\frac{sin(a)-sin(b)}{a-b}$
\
$cos(c) = \frac{sin(a)-sin(b)}{a-b}$
\
but $-1 \leq cos(c) \leq 1$
\
so
\
$-1 \leq \frac{sin(a)-sin(b)}{a-b} \leq 1$.
\
we now multiply across by $(a-b)$
\
We thus get
\
$-(a-b) \leq sin(a)-sin(b) \leq a-b$
\
$sin(a)-sin(b) \leq |a-b|$
A dense set
This is what I've done so far
Can you simply multiply by (a-b) without affecting the inequalities tho
$a-b$ is positive
A dense set
it says for all a and b?
Actually I cannot read, you assumed a > b mb
I mean by the acrhemedain property, for every a there is a greater b, that enables me to cover all a,b
Got it
thanks
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$f(f(x))=\frac{x^5+5x^4+10x^3+10x^2+5x+1}{x^3+3x^2+3x+1}$
if $f(1)=3$ then find $f(25)$
Skill_Issue
i noticed that the fraction can be simplified to $x^2+2x+1$ but im not sure what next
Skill_Issue
what
f(3)=4
f(4)=16
think so
not 25 tho

fr idk how to continue
envien ph
@viral dagger Has your question been resolved?
Wait f(f(4))=25, so f(f(f(4)))=f(25)
And you can find f(f(f(4)))
It’s (f(4)+1)^2
So it’s 17^2
@viral dagger
how did you get this
f(f(x))=(x+1)^2
oh
isn't another way to say
you know f(4) = 16
so f(f(f(4))) = f(f(16))
then you can plug into the equation for f(f(x)) givne
idk
Yeah
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Is this proof too terse
We wish to proceed via induction
\
Base case : $\sum_{k=1}^{1} \binom{k}{r} = 1$
\
Inductive hypothesis $\sum_{k=1}^{n} \binom{k}{r} = \binom{n+1}{r+1}$
\
we wish to prove that this implies that $\sum_{k=0}^{n+1} \binom{k}{r} = \binom{n+2}{r+1}$
\
\
$\sum_{k=0}^{n} \binom{k}{r}+ \binom{n+1}{r} = \binom{n+1}{r+1}+ \binom{ n+1}{r}= \binom{n+2}{r+1}$
\
This concludes our proof
yes this works 
have you seen rudins books?

A dense set
That's the book
c(0,n)=0
so thats how its defined
oh wait that's the same as not choosing anything why did i not think of that...
your base case here doesn't make any sense
or wait maybe it does
ok nevermind it works assuming the restriction in the question that isn't actually necessary for this result to be true
@twilit field k=1 in base case
with r=0 both sides evaluate to n+1, with r > n both sides evaluate to 0
so there's no actual reason for the condition that 1 <= r <= n
We wish to proceed via induction
\
Base case : $\sum_{k=1}^{1} \binom{k}{r} = 1$
\
Inductive hypothesis $\sum_{k=0}^{n} \binom{k}{r} = \binom{n+1}{r+1}$
\
we wish to prove that this implies that $\sum_{k=0}^{n+1} \binom{k}{r} = \binom{n+2}{r+1}$
\
\
$\sum_{k=0}^{n} \binom{k}{r}+ \binom{n+1}{r} = \binom{n+1}{r+1}+ \binom{ n+1}{r}= \binom{n+2}{r+1}$
\
This concludes our proof
A dense set
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q is to evaluate this integral
Sho
am i just bad or are ans wrong
lol this is correct
-ln|x|=ln|1/x| you forgot about the - sign in your answer it is supposed to be -2ln|cosx/2|+c @drifting root
AHHH
Thank you, i was so confused cause i copied it down as cos in class as well
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im. not too sure how to begin
Wait a Min
those are some big numbers
let's work with a simpler problem first:
if A takes 2 hours to fill a bathtub, and B takes 3 hours to fill a bathtub, how many hours does it take when A and B both fill the bathtub?
hint: think of how many bathtubs A and B fill in 6 hours
chatgpt
!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.
yea yea
yeah
do the normal way
the trick way is so coool though but
he/she may get confused
yeah if you only know one way, do the normal way
yeah I can get to the trick way from this
normal way has more use
it generalises really nicely if you cancel out the 6 in the numerator and denominator
denominator is ||6/2 + 6/3||
yeah
i think this is a good way to start, either way, too :p
is the answer 6/5 hours? i've completely forgotten about inverse proportions
yep!
alr thnx!
does it take
work = rate x time right
yeah
so 1 bathtub = 2hr/bathtub x 2hrs
the other one would be
1 bathtub = 3hr/bathtub x 3hrs?
$\frac{2 hr}{bathtub} \times 2 hr$?
Ginger
is the left fraction the right direction?
yeah, now that's correct
1/3 barbeques per hour yes
yeah so 1 hour = 1/2 bathtubs and 1 hour = 1/3 bathtubs
you're not doing bad
wait no
k so their rate together is
"1 bathtub is 1/2 hours" would correspond to 2 bathtubs every hour, not 1 bathtub every 2 hours
yeah I confused myself
5/6 bath rubs na hour
hold on let's get the correct equation from what you did
simultanous in CAS
5/6 baby back ribs per hour
H bz z .!? hrrngh
so now 1 hour = 1/2 + 1/3 bathtubs
okay so now what is 1 bathtub
1 bathru = 5/6 bath/hr x T
6 abth = 5bath/hr x T
what the gell am i doing
takes 6/5 hrs
?
what are you guys talking about with bathtubs
breaking down this rate problem
we're talking about barbeques
is it 6/5 hours
once you can do it for 2 bathtubs, it generalises really nicely
yep
so it is actually 1/(1/2 + 1/3) and you can simplify that to 6/5
Hey Im new to this server
can i resent the og provlem here
try convincing yourself that if A takes 2 hours, B takes 3 hours, and C takes 6 hours
then it's 1/(1/2 + 1/3 + 1/6)
cause 1 hour = 1/2 + 1/3 + 1/6 bathtubs
and now divide by the same thing on both sides to find ? hours = 1 bathtub
welcome
yep!
so nearly there, if you add all the people up in the original question, you get 2 * (M + A + T + H)
abthrjudb
wait wait wait
this was kinda the "trick" method to me (x but yes it's nice
ok then
wgat
so if you want to find the time taken for just (M + A + T + H)
what must happen to the time?
there is twice less manpower but the same work to do
divide 2
no, the time wouldn't be quicker
time s2
wait really their names spell math
this keeps getting deeper
yeah lmao they do
someone posted GPT output and I realised
that is amazing lol
remember this?
12008 rate
do the exact same thing for these 4 people
(4 pairs of people)
like you can treat M + A as one person
and A + T as another person
ok idk if this helps like
Mathis and Anders
- Andres and Tellis
- Tellis and Hal
- Hal and Mathias
all working on it at the same time. so yes they ahve twins
A T takes 1/1540 TH TAKES 1890 and hM takes 1/1386
so the time it takes
for all of then togthehrr is
god do i need to multiply them
no it's the bathtub thing
i know but
1/2, and 1/3
wait what are you calculating tho
is a calculator not allowed
no
the answers are in decimals
no calculote
😠
I CANT USE
or with not a headache
just find the expression, don't worry about the no calculator bit
actually the super trick method is that you know you need to multiply by 2
so it has to be D, cause 364.7 * 2 = 729.5 nearly
only A and D are separated by a factor of 2
How
🪦
2 * 1/(1/1188 + 1/1540 + 1/1890 + 1/1386) to be exact
bc he knows the test creators will try to trick you
by creating one option that is if you forgot to multiply by 2
Shit SHIT
but then that's not teaching you about maths
that's just teaching you how to get good at MCQs
if it's short-answer where you need to show work you'd be screwed
so this is the problem done
pretty much
yess
yes
each 4 individually
so the rate of the 4 dupes are
just 1/however long takes them to fuck
but that means its 2 times the speed of the actual 4 people
so if we want how fast to do 1 peach but with half the manpower
u need to fond 1/shit and muiplty the time it takes by 2 since half less people
this is the first time i'm realizing the original problem is about peaches
yr allowed to times half less people becaus it loses each dupe but IF IT LOSES not a dupe it fucks the proboke up
right
what the ||fuck|| is gaffney peach
I dont fakign know
is this right
yeah that sounds right
Ok
it's the same as dividing by the rate by 2
before you do the 1/everything
anyway yes
sounds good
i can try
interestingg
i'm not a mathematician
i might be too dumb for this one
without hints
Fuck
but now i'm probably going to keep thinking about it
the other one seems easier to me
Shit
i'm thinking about the wording actually
let me check something
,w 1 - .4 - .6 * .4
,w 18/25
ok so
they. jus tmean
what is the probability that alejandro won?
ok i can do this one
but idk if i can do it in a simple way
yeah
that sounds similart to what i was thinking
there are two "groups" of cases
well you can think about it however lol
there must be a faster way tho no?
cuz they expect this solved in 2 mins
until the double win
eactly
hmmm
this way maybe could be done quickly?
idk sounds like a lot to me
group 1 is like: start with .6^2, then multiply by .6*.4
unless u can simply some cases
group 2 is .4 multiplied by group 1
wait where are these questions from btw
group 1 = .6^2 * 1 / (1 - .6*.4)
wait its a geometric sequence no?
my teacher
just wrote the formula for that. exactly
yeah these look a lot like contest maths
wait wai
can you ru. me thorugh the logic again
i gtg
@fleet axle
so we have 2 groups one is if he jusy wins in the 2 rounds
and other is alternating and then he wins
it always alternates so
you have 2 geometric series
one is if he wins first
other is she wins ifrst
but then it always laternates
if he wins first its
and ends with him winning
0.6 x 0.6
so, the series where she wins first, the whole thing, is just 0.4 X the series where he wins first
but there's a whole series, so, 0.6^2, or 0.6 * 0.4 * 0.6^2, etc
0.4 x 0.6 x 0.6
one more 0.6 here
0.6 * 0.4 * 0.6^2
the common ratio is
i see
right cause
Group 1: (he win)^2, or (he win)(she win)(he win)^2, orrrr (he win)(she win)(he win)(she win)(he win)^2
Group 2: Same, but add an extra (she win) in front of everything
i see
ok so
win is always 0.6 squared
but they alternate
every 0.6 and 0.4
which makes that the common ratio
rightt
and theres 2 ways
one is first he win the other is
lina go first
soi just add the two cases
ok i grg cya
tysm
.close
yes [erfect
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cna I have a hint for (b)
I've tried playing around with some inequalities
but that doesn't help much
like $e^x \geq -(1+x+x^2/2)$
A dense set
e^x>1+x-x^2
@twilit field Has your question been resolved?
A dense set
what tools do you have available?
MVT, rolle's theorm and the first and second derivatve tests
and differential calculus
compare the derivatives
$e^x \geq 1+2x$
A dense set
isn't always true
check again
let x=1, $e \ngeq 3$
A dense set
check your derivative again
1+x is the derivative
e^x is always more than 1+x
oh right
okay
thanks
I suppose i can use the same for the last problem
Thanks!
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This is physics and not math
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Trying to prove this
The lower bound I have is $2\sqrt{2}$
A dense set
as per my calculations
How did you get to it?
using this property
Ah, that looks to weak
Hint: $x^2$ is always lesser than $\sqrt{x^4+1}$
yeah, that's probably it
you can just remove the one inside and figure it out too
just 4 months ago, I would have figured this out in a snap 😭
i got lucky guessing the function though 😂
,w \int_1^3 x^2
yup
i saw 26/3 = 27/3 - 1/3 and thought it was x^3/3
works only sometimes though
A dense set
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thanks
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is (-1)^(1/3) = -1 or 1/2 + i√3/2 ?
Depend on the context
Context is whats around the question.
The principle root?
the principal root is the root with the biggest real part
bprp has a video on it
what about the imaginary part?
doesn't really matter
because there is also 1/2 - i√3/2
link pls
principal root is essentially the root of unity with lowest arg
so it is 1/2 + i√3/2 ?
for instance n_/x means the nth principal root of x in most contexts.
WolframAlpha gives different results if you try the cube root of -1 versus taking -1 to the exponent 1/3. Why is this happening? There is a good reason for the difference, which involves complex numbers and roots of equations. Special thanks this month to: Kyle, Lee Redden, Mike Robertson, Daniel Lewis. Thanks to all supporters on Patreon! http:...
its presh actually, not bprp
so (-1)^(1/3) is not -1
🙏
?
my objectif is to know the domain of x^x
what I want to know is for exemple (-1/3)^(-1/3) is real or not
@oak granite Has your question been resolved?
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How did you solve itt?
What how
ohh nvm
but, is 6 correct tho?
Nuh
hmm wrong theorem then
I solved it by using similar triangles
So BD = EC
How do you know that?
ED=EC=CB
okay so ED = DC = CB
Yep
AD cuts the EB line in a place, name it G
Same for AC , name it F
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** High School Math Question **
Define ${f: \mathbb{N} \rightarrow \mathbb{N}}$ such that ${f(x) = x^3 + 2}$ and for any positive integer ${n}$, define:
\begin{enumerate}
\item $f_1 = f$
\item $f_{n+1} = f \circ f_n$
\end{enumerate}
Find the number of integers ${x}$ over the closed interval ${[2023, 2566]}$ such that $(f(x))^{f(x)} - f_{f(x)}(x)$
k
Answer key: 271
i have the full solution but i dont understand it
and it's in my native language
What language?
thai
my attempt at translation
i dont even understand
this notation tbh
<@&286206848099549185>
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why is this wrong
'perimeter'
which would be pi(r) in this case
wht m i meant to do
do i find the sector?
do you mean arc length?
yh
sure
wht do devide 360 by
since its half a circle we can just do this
half the circumference of a whole circle
so pi/2?
arc length
x/360 * 2pi*r
yeah can be used
arc lentgh/theta = r
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Optimization -- minimum distance between two points
Find the point on y^2 = 2x that is closest to (1,4)
d = sqrt (x-1)^2 + (y - 4)^2
x = 0.5 y^2
d = sqrt (0.5y^2-1)^2 + (y - 4)^2
then instead of minimizing d, the textbook says to minimize it's square so
d^2 = f(y) = (0.5y^2-1)^2 + (y - 4)^2
why do you square everything?
I get that squaring d removes the sqrt . But why do we change to d^2
Because working without roots is (usually) easier. And in this case minimizing d or d² is the same, because you're finding the point that minimises d, and not the minimum of d
And note that his works because d is non negative, as d² is
And in this case minimizing d or d² is the same
how can I know this, I don't want to always assume
my textbook says "you should convince yourself that the minimum of d occurs at the same point as the minimum of d^2, but d^2 is easier to work with"
Exactly, indeed
Well, if d is the minimum it means that d < D for whatever other distance D you consider
If you square this you get d² < D²
So d² is the smallest among all other distances square
Note that I'm not saying that the the minimum d has the same value of the minimum d²
so if I find the minimum of d^2 it is the minimum of d?
In other words d can be different from d². What matters is that d and d² are the minimum at the same point (x, y)
Yeah, if you find for instance that d² has minimum value of 3, it means that the minimum value of d is √3
The key concept here is that minimum ≠ point of minimum
i'm trying to sketch it out, sorry I don't fully get it
we want to find the (x,y) (blue) where distance (d orange) is the smallest
You can't actually visualise d²
Or better said, it doesn't have a geometrical meaning in this case
The fact is that you can do that because d ≥ 0 and on d ≥ 0 the function d² is monotonically increasing
You simply don't
No no
It's something quite trivial, I don't actually know how to explain it
I think I'll close this for now, if you know of any resources or have an idea for an explanation would you mind pinging me or dming me?
Thank you so much
I think you can wait for other helpers, before you close the chat
Probably some helpers turn up, they might be going around here
Sounds good I can wait
I am currently trying to understand
- How d^2 can be understood in the pinned equation
- Why does minimizing d and d^2 occur at the same point
I'll tag helpers, so that they know they can directly read the questions here
<@&286206848099549185>
thank you :)
https://youtu.be/lx8RcYcYVuU?t=2670
I followed along to this and noticed that he did not ignore the square root. I tried seeing what happened when I did and there was no change in where D = 0 since the deriving the square root divided everything in the numerator by 2 and since the numerator determines where D' = 0 that seems to make some sense. (this doesn't fully resolve the questions, but I think is helpful)
I personally just set
D^2' = 2(7-x)(-1) + 2(2+x)
= 4x - 10
x = 10 / 4 --> 5/2 (when set to 0)
he has the same ratio except divided by 2, which I guess is negligible in finding the critical point
and the denominator can never be 0 since you are adding two squared numbers, so d^2 is defined in all real numbers
im confused too now
Yeah exactly, here when you solve derivative = 0 you can eliminate the denominator, which actually is the derivative of the inside of the square root, due to chain rule. But what is inside the square root? If you think about it for a while, it's exactly d^2
You spotted on! We're not interested in the value of d (or d^2) but rather in the value of x that makes d have the minimum value (whatever that value is)
I think you're getting it now 👍
sorry I basically noticed that d^2 is the same as the numerator of the derivative
though technically it's 2* greater, you can factor it out and it's ignored in critical points
thank you both, I'm still a little scared for the test but it's decreased today XD
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Is it right?
Find (f(x) = (-2)?
Did you mean f(x) = -2?
Then it's wrong
I see so it's probably F(x) = -2, where F(x) is the derivative of f(x). So it's still wrong.
Yes
Send the original question
F(-2)
F(-2) and F(x) = -2 mean two different things
,rotate
So it's not derivative
Its function
So your answer right
Wait the first one isn't correct calculation
The result is correct but a step wrong
Should be -4 not +4
Try factoring more
