#help-27
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for example if you get f(1) = -4, what do you add to get 2?
-2?
-4+_=2
6?
for the second term here i get 1/4=c and n=4?
dont forget about the negative sign
so its -1/4?
so my equation shouldve been -x^3 = cnx^n-1 ?
the last term is just x?
i got
f(x) = (1/2) x^2 - (1/4) x^4 +x
right, but we also have a really important +C
remember how 3x+5 and 3x+7 have the same derivative?
yes
so my equation is
f(x) = (1/2) x^2 - (1/4) x^4 +x +c
then i sub in f(1)=2?
for this one theres they give me two to plug in
do i do that the same way?
notice that you have f''
you have to be a little careful with this one
first we find f' by finding the function that has the derivative equal to f''
what function has a derivative e^x
part A i got
f(x)= (1/2)x^2 - (1/4)x^4 +x +3
c=3?
e^x?
yes
3 doesnt sound right
-3
when you have f(1) = 2, you replace all instance of x with 1
on the left, you have f(1), which you can replace with 2
and on the right, you have (1/2)(1)^2-...
thats better
f(x)= (1/2)x^2 - (1/4)x^4 +x +(3/4)
thats my final equation?
yup
this one i got
f(x) = x + 2x^(3/2) +c
and then i solve for c?
yup
the second term is ok ?
looks right
and then for the last one , is f'' the same way to solve?
i have to do it twice?
yes
just 2cosx
you only need to worry about product rule if the two factors are both functions
if one is a constant, you dont need to worry
dont forget the +C
i dont have to solve for f(x) first before i do the +c?
but i want you to write it as $C_1$
me when the gbf
so i sub it in twice with f(0) for c1 and then f(pi/2) for x2?
not yet
first off i want you to be careful with the -2sinx part
derivative of cosx = -sinx, so the minus sign turns into a plus sign
so it would be +2cosx?
and then i sub in f(0)=3?
we are working backwards, so the derivative of what becomes a constant?
wdym?
using the reverse power rule method or any other method, the derivative of what becomes C1?
cx?
yeah C1*x
f(x)= e^x -2sinx +c1x ?
watch your signs on the trig function again
derivative of what function becomes +cosx? is it +sinx or -sinx?
+2sinx
another constant?
we add c2 to the end of that equation?
yup
then you can plug in your function values to get a system of equations to solve for C1 and C2
one at a time?>
wait wdym
plug in x=0 first
this will get rid of C1, because C1*x = C1*0 = 0
no system of equations needed
just some algebra
c2=2?
yup
because it gets rid of the c1x term
would it be wrong if i pluged in f(pi/2)=0?
if you plugged in pi/2, then both variables are there and you cant solve anything
i should say unknown constants, not variables
do i always plug in the first one or i have to know which one to plug in?
you could plug in either first, and then youll find out which one is more useful
you may find both are not too useful, but together they form a system of equations to solve them
yes
i plug in the f(pi/2)?
yeah, plug in x= pi/2
How would I solve this?
you can leave it in exact form or approximate it by plugging it into a calculator
it has no clean answer
I got this?
,calc (-e^(pi/2)-4)/(pi/2)
Result:
-5.6089241047199
looks right
my final equation
f(x) = e^x + 2sinx -5.61x +2
looks good
youre welcome
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simple question, for part c what does it mean by initial depth?
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Two rectangles have areas in the ratio 36:121. If the length of the smaller rectangle is 15cm, what is the length of the bigger rectangle?
Just wondering if I’ve gone wrong here
Since the answer is irrational
<@&286206848099549185>
<@&286206848099549185>
all caps when you spell the mans name
Is my Spotify status still visible?
no
Oh
ur name is a dead giveaway
Yeah
So just checking I haven’t done a step wrong
I feel like I have but I can’t tell why
the ratio between the sides and their areas arent the same i believe
My answer is irrational and I feel like it shouldn’t be so I’m running around in circles trying to figure out what I did wrong
Well if the ratio is 36:121
And the smaller side is 15cm
Wouldn’t it make sense to cross multiply
?
K
is the question assuming that they have the same heights?
Well that’s all the info given in the question
If the height on the smaller triangle was 36cm (hypothetical) than the height on the bigger rectangle would be 121cm since that’s the ratio
thats not what im asking
Oh
the height of the smaller rectangle is 2.4cm so are we assuming that is also the height of the larger rectangle?
There’s no given height?
And the heights of the two rectangles would correlate to the ratio 36:121
Wait I just realised
yeah but thats my problem, the areas are in a ratio
uhh ok
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im not sure about how i would start question D
@stray ravine Has your question been resolved?
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this is rational function and i am not sure about the graph im just posting here just to check the graph
not quite
look at values close to -1 and see what happens
and you're y-axis isn't consistent
the y-markings are not uniform
meaning having the same difference
for a normal graph the difference in nearby markings would be same
you would get a function like this if plotted properly
just one more thing
yeah wahts up
maybe try marking the graph with y axis marked as -1, -0.5, 0, 0.5, 1... and then drawing the graph
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Let the family set Ai with i ∈ N ∶ Ai =] - ∞, i]. Show that ∩i∈N Ai = ⋯
is ∩i∈N Ai = (-inf,0]?
@vast quiver Has your question been resolved?
@vast quiver Has your question been resolved?
@winter torrent
i think that's probably fine, although I'm not sure I believe that line 3 implies line 2
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how do i solve these two quesitons?
im confused
f is a simple enuf function
I think u can sketch what the integral of that looks like
0_0
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hi
could you please give me a hint for this
here is how far i could go
btw
i made a mistake
why did you substitue x = 1 - e^4
you should follow a rule
that substitute a function whose derivative is present
try again using that again
i tried that but nothing came to my mind
1/x is deriv of ln (x)
the only thing that might work is this ig
do you know what is the derivative of ln(1+x)
1/(x+1)
all good
sorry
idk how to use it ):
if its the only way then i should move on
huh
Li(x)
In mathematics, the polylogarithm (also known as Jonquière's function, for Alfred Jonquière) is a special function Lis(z) of order s and argument z. Only for special values of s does the polylogarithm reduce to an elementary function such as the natural logarithm or a rational function. In quantum statistics, the polylogarithm function appears a...
this is so cool
I don't know which sub to take but I only know using series
should we use series to get this ?
its all good man tysm
I don't know lol, I just shared you a source assuming you know it
to match that form
LOL tysm
this is way beyond my knowledge
Alaska
ok ok
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then you divide by x
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How can I quickly tell if this matrix has independent columns?
and how can i see which columns are not independent?
consider whether 4 vectors in R^3 can be linearly independent, generally
so i can just chose any column?
it's not necessarily obvious whether any column could be removed to make the columns linearly independent. a systematic way would be to compute the REF
hm okay thx
do you know how i could do the "The Strang Decomposition A = CR" on this?
i believe you start by taking the RREF of the matrix in question
idk i never heard of this
RREF
i prob wont have enough time to do all these steps anyway in the exam lol
there has to be a trick
you haven't heard of reduced row echelon form?
this ?
yes
yeah im confident u can do this without using RREF
the prof also said that we wont have time to do calculations
so yeah
the "R" part of the A = CR decomposition is the rref of A (0 rows removed) so i'm not sure how you would do that
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Do they mean probability of 1st success of 7 MORE trials after the 5 failed trials(same for 2?)?
No, 2 more trials for a total of 7.
@plucky maple Has your question been resolved?
Wait lemme process
Ohh my god
Of course yeah that makes sense
Ty so much
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!status
What step are you on?
1. I don't know where to begin.
2. I have begun but got stuck midway.
3. I got an answer but I was told that it's wrong.
4. I got an answer and would like my work checked.
5. I have a question about someone else's work/solution.
6. I have completed the problem and don't need help anymore. Thank you.
7. None of the above
1......
@covert umbra Has your question been resolved?
Start by multiplying by $\dd x$ you would get the form
[ \underbrace{\left ( 2y^{a+2}+3\sin x \right )}{M} : \dd x + \underbrace{(10y^4x+e^{ay})}{N} : \dd y = 0. ]
Now recall, the differential equation is exact if and only if
[ M_y = N_x ]
𝔸dωn𝓲²s
what does My mean
partial derivative wrt y
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i solved and got 2 for the value of k
now orthocentre is equidistant from all the vertices
so i took ortho centre as (x', y') and did using distance method
but unable to get the ans using that
Maybe just compute where 2 altitudes intersect?
yea that is another way, but isnt this logical too??
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Hello!
I have the following "table" and want to calculate this:
I know that the solution would be this:
I don´t know where to start 
Do you have any additional context?
no, sadly not
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Consider the infinite series
[
\sum_{n=2}^\infty n^{-1 - \frac{1}{(\log_2 n)^2}}.
]
Determine whether the series converges or diverges and prove your answer. Use a dyadic partition.
ZaoWuZhu
Broke it into the dyadic partitions, but struggle to see what to do after
I dont know what a dyadic partition is but I see that the series is greater than 1/(n log n) which is divergent. That's because 1/log n < loglog n.
@warped prism Has your question been resolved?
Yeah, I know it diverges
but really not understanding how to procede from the the partition
[
\sum_{n=2}^\infty n^{-1 - \frac{1}{(\log_2 n)^2}} = \sum_{k=1}^\infty \sum_{n=2^k}^{2^{k+1} - 1} n^{-1 - \frac{1}{(\log_2 n)^2}}.
]
ZaoWuZhu
Let ( S_k ) denote the sum over the ( k )-th dyadic interval:
[
S_k = \sum_{n=2^k}^{2^{k+1} - 1} n^{-1 - \frac{1}{(\log_2 n)^2}}.
]
ZaoWuZhu
I think, if you substitute n with 2^k, you can a lower bound for S_k. Like S_k > 2^k * (2^k)^(-1-1/k^2)), the first 2^k is the number of summands in the sum.
This simplifies to S_k > 2^(-1/k), and the sum over k diverges for k-> infinity.
The series can then be written as
[
\sum_{n=2}^\infty n^{-1 - \frac{1}{(\log_2 n)^2}} = \sum_{k=1}^\infty \sum_{n=2^k}^{2^{k+1} - 1} n^{-1 - \frac{1}{(\log_2 n)^2}}.
]
Let ( S_k ) denote the sum over the ( k )-th dyadic interval:
[
S_k = \sum_{n=2^k}^{2^{k+1} - 1} n^{-1 - \frac{1}{(\log_2 n)^2}}.
]
For ( n \in [2^k, 2^{k+1}) ), note that ( \log_2 n \geq k ). Thus, ( \frac{1}{(\log_2 n)^2} \leq \frac{1}{k^2} ), and the terms in the interval satisfy:
[
n^{-1 - \frac{1}{(\log_2 n)^2}} \geq n^{-1 - \frac{1}{k^2}}.
]
This gives a lower bound for ( S_k ):
[
S_k \geq \sum_{n=2^k}^{2^{k+1} - 1} n^{-1 - \frac{1}{k^2}}.
]
Since ( n \geq 2^k ) within the interval, we further bound each term by ( (2^k)^{-1 - \frac{1}{k^2}} ), giving:
[
S_k \geq (2^k)^{-1 - \frac{1}{k^2}} \cdot \left( 2^k - 1 \right).
]
Simplify:
[
S_k \geq (2^k)^{-1 - \frac{1}{k^2}} \cdot 2^k = (2^k)^{-\frac{1}{k^2}}.
]
To simplify ( (2^k)^{-\frac{1}{k^2}} ), use the identity ( a^x = e^{x \ln a} ):
[
(2^k)^{-\frac{1}{k^2}} = e^{-\frac{k \ln 2}{k^2}} = e^{-\frac{\ln 2}{k}}.
]
As ( k \to \infty ), ( e^{-\frac{\ln 2}{k}} \to 1 ), so:
[
S_k \geq C,
]
where ( C > 0 ) is a constant independent of ( k ).
To prove divergence, we compute the total sum of the first (N) dyadic intervals:
[
\text{Partial sum: } \sum_{k=1}^N S_k.
]
Using the lower bound ( S_k \geq C > 0 ), we find:
[
\sum_{k=1}^N S_k \geq C + C + \cdots + C \quad \text{(a total of (N) terms)}.
]
Simplify:
[
\sum_{k=1}^N S_k \geq C \cdot N.
]
Since ( C > 0 ) is constant, the partial sums grow with ( N ). Letting ( N \to \infty ), we see:
[
\sum_{k=1}^N S_k \to \infty.
]
This shows that the sequence of partial sums is unbounded, and the series diverges.
The series
[
\sum_{n=2}^\infty n^{-1 - \frac{1}{(\log_2 n)^2}}
]
diverges because the partial sums grow without bound,
ZaoWuZhu
I tried to flesh it out a bit
Looks good.
@warped prism Has your question been resolved?
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I feel like I have an idea of where to start; however, I would like some assistance
explain your idea
So my thought is firstly, finding the Eigenvalues of A, then finding the Generalized Eigenvalues to then use the General Solution form
So, then you would have eigen-values of -1 with multiplicity three
And then you have eigenvector (1, 1, 1)?
Wait wait
Nope, I have no idea
Wait
Yeah I have no clue just because of the repeated Eigen Values
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Just need quick and simple help, i understand the question however the only thin i dont understand is how where 2x-1=ln(50), the -1 moves to the other side, dont you have to add 1 to each side meaning it would be 2x=ln(50) +1 ?? sorry if this is very simple just going over my basics
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Hallo I need an explanation why these are the formula when finding FV and PV in compound interest.
I'm confused how we will get PV if we need PV to get FV
Nvm there will be a given for FV
I just need an explanation why division and multiplication
NVM I got it... I just need to divide it both sides by the parenthesis
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I want to redefine this dot product using the definition involving the magnitued of the vectors and the ange between them
should I keep or discard the negative?
I imagine discard? Like it's basically just flipping the mu vector
the negative should still be there
if you flip the mu vector that changes the angle
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what is the technique called that allows you to do this kind of math by hand without a calculator? 11^5 mod 13
11 is congruent to -2
that's great but how does that answer the question?
I think it might be "square and multiply" @faint gorge
sounds correct
there's also Hensel's lifting lemma if you are interested
I am interested in the simplest and quickest solution
which with a name like that I think I will stick to the first
if you want to find say 11^5 mod 13^2 or 13^3
but yeah the simplest is just (-2)^5 = -32 = -32 + 39 = 7 mod 13
thanks
no worries!
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help please I am getting 0 as an inflection point and as a critical point and when I test with the first derivative, there is a change in sign which means it should be a critical point and at the same time I also got it as an inflection point. However in my answer key it says that the answer is E
@proven grove Has your question been resolved?
<@&286206848099549185>
find where the first derivative is equal to 0
then find where the second derivative is also equal to 0
if they are at the same point than count it
i did that
first deriv = 0 @ x = 0,1/3
second deriv = 0 @ x = 0,1/4
and i tested 0 and it changes
from pos to neg
around the point
but the answer key i have says that no critical points are the same as inflection points
@proven grove Has your question been resolved?
Test this for second deriv. If it's an inflection point, then there is a change in the sign of f''
@proven grove Has your question been resolved?
i tested it and it does change
but the answer key says that there are none inflection points that are also extrema
here is the graph in desmos
An inflection point must show a change in concavity, what do you see in the graph? 🤔
also what I meant is that you should check if the sign of second deriv changes
I mean there’s a slight dip but idk
also it’s a no calc problem i wasn’t even supposed to be graphing it
ye I did that
it changes from concave down to up
1/3 is past another point where f'' is 0
try a smaller interval
I mean, the points where f'' = 0 are x=0 and 1/4 as you calculated
If you want to check change in sign for x=0, don't check a value greater that 1/4
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Hey! How to multiply
how to multiply what
@rancid spire Has your question been resolved?
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why does labda become 1
what does the eigenvalue show
like what does it actually mean
the scalar right
Yes
How much everything gets scaled by
If you look at the first line
There is no scaling happening
So its lambda = 1
Remember Ax=Lamdax?
ya
Well theres the Ax on the right hand side
and the lambda x on the other side
And as you can see there is no scalar value
so lambda is just one
you follow me?
uh not rly
why dont they write lambda in the first place
Ax= lambda x
i understand this much
Because it says the number of visitors is constant, so if lambda was there it would mean that its not constant
and when lambda =1 it becomes Ax= x
as every transformation would scale up or down the number of visitors
x = the vector with GIM, and do you see a constant in front of the vector on the left hand side of the side equation?
no
So what must the scalar be?
1
There you go
Let me explain like this
imagine you have kid, adult and elderly visitors and you use the vector they gave to represent it
and imagine the transformation aka matrix-vector multiplication with A is applied every day to get the next days number of visitors (kid, adult and elderly)
And it tells you that the number of visitors is constant
so there cannot be any scaling
The eigenvalue shows how much the eigenvector gets scaled by
therefore the eigenvalue must be 1
Is this clearer?
only the total (kid , adult, elderly visitors) remain the same but the individual visitors of each category changes ?
No, every single one remains constant
this part multiples with identity matrix to factorise [G I M]?
Yes because you can't subtract a matrix and a scalar so it can't just be A-1 you need the identity
ok thx
All clear?
watch 3b1bs essense of LA it clears up alot of stuff
Whats the chapter
eigenvector and eigenvalues
you take a levels by any chance?
I see
Then why you doing this, its FP2?
im in uni
do some research on eigenvector convergence
egineering maths shi
so this chap is basically new to me
college math basically
only standard a level maths
not the further maths
same tbh, I learnt it a couple months ago, 3b1b's videos helped so much
youtue?
would highly highly recommend
yes, watch his playlists on the essense of linear algebra and calculus
what uni you in?
if you dont mind sharing
Im in y12
still got a while
college at?
Eyeing trinity maths
u took further maths?
Im taking right now
oh nice
Exam is next year
i dropped it after a few months lmao
I have to take it cause I wanna study maths 💀
but our school picked further stat and mech
which I hate
well if u like maths den go ahead
No its optional in FM
huh
school chooses 2 from 8
there are 8 papers
FM1 and 2, FS 1 and 2, further pure 1 and 2 and decision 1 and 2
school picks 2 for you
my college set it for us, basically AS do further pure and further stats, A2 do further mechanics and furher pre
same ig
u in A2?
We re doing AS topics rn in school but Im doing A2
thats a high aim
they did this in primary
Im obviously joking but they're still really cracked
anyways i gotta get some work done
good luck with your eigenvalues and vectors chapter
cya
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Can some pls explain example 38.1
I want the example explaines not the exercise
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Can anyone pls explain example 38.1 pls
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you have two right triangles and they're congruent by hypotenuse-leg
Oki
In the book if zayz
AB is a chord of the circle,centre O
X is the midpoint of AB
OA and OB are radii,
So truangle OAB is iosceles
OX is a line of symmetry for triangle OAB
Therefore OX is perpendicular to AB
This shows that
The perpendicular from the centre to a chord bisects the chord
How does that apply in the example
well that perpendicular part gives you the right triangles
I get that AB is a chord
OA and OB are the same length
But OBA
the chord bisection doesn't matter so much since they told you it's the midpoint already
what about OAB?
Sorry OBA
right, we have to right triangles
How is OAB and AOB same
they share the hypotenuse (radii) and a leg (OX)
Mhm
there's a hypotenuse-leg theorem for right triangles which says they're congruent
Ok
then you can use CPCTC (corresponding parts of congruent triangles are congruent)
Ok
that should be it
Ok.thank u very much.have a nice dayy
thanks you too!
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I did the ratio test to find the convergence for this power series but I’m not really sure at this point?
@oblique mulch Has your question been resolved?
you calculated 1/R = 1/2 so it's actually R = 2
also check end points
assume x = 2 and look what series you would get ...
why 1/R?
Interesting
so I should be taking the ratio test upside down with an above an+1?
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explain your work
give me a sec
this should be really easy to double check
oh wait
its 3
hahaha im stupid
wait no
nah ill respond back in a sec
no
ok now im even more stupid then stupid
the answer is 2
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3b anyone?
did you try proving it when I = [a, b]
@blazing crest Has your question been resolved?
idrk
@blazing crest Has your question been resolved?
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@blazing crest Has your question been resolved?
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Good morning, if we have two uniform distributions D1 and D2 bounded by B1 and B2 respectivelly, can we have a relation between the bounds such that the two distributions are indistinguishable?
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@cerulean wharf Has your question been resolved?
Hmm B1 and B2 must be very close because the min entropy differs by an exponential 😔
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Have I done this right?
i think i need to add b + a = RHS, but there's no answer so i'm not sure.
@hexed holly Has your question been resolved?
Seems about right. The + law is commutative in the real or complex ring so when adding two 3 dimensional vectors it boils down to doing 3 normal additions like you did.
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Hey ! Can anyone help with finding the ways to resolve the first integral ? I am kind of stuck
if you solve for y (or x) in the conditions you can turn this into a calc 1 problem
at least for part a
x^2 = 2y
x^2 = 1 + y^2
1+y^2 = 2y
y^2 - 2y + 1 = 0
(y-1)^2 = 0
y = 1
x^2 = 2 -> x = +-sqrt(2)
@north pivot Has your question been resolved?
This is what I found
but when i write the integral down it seems unclear on the limits
wdym
i'd say the easiest thing here is to use the symmetry of the region
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sure
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Let V be the volume of the solid obtained by rotating the region bounded by the curves y=(tan(x))^3, x=π/6, x=0 and y = 0 about the line y = 2
great i forgot how to use latex after years uh
this
i got a and b correct but i dont know why is this wrong
please enlighten me
thx
oh, nvm
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just want some confirmation on this
I did evreything now for the helicopter off the ground
would I just do 661sin 28 degrees 11 and 445sin 44.5 degrees
@restive river Has your question been resolved?
<@&286206848099549185>
There are three interior angles in a triangle
U know 2 of them
Find the top angle by doing 180-first angle - second angle
Then use the sine law to find the lengths of the legs of the triangle
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how do i solve this
solve sin(t) = sqrt(3) / 2 for t first. then solve t = x/4 + pi/3 for x
definitely more than 1 solution for x
sorry, what do you mean by sin(t) = sqrt(3) / 2 for t first
By t what do you mean?
t is another variable
ok and what about this:
,tex .shift trig
riemann
either top left or one beneathe it
beside this any other method?
my teacher asks me various method, he might ask me to do another way
and the test is tomorrow
😭
ofc if there IS another way.
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help
can sum1 tell me if the power point is ok
sus
and be honest
it could easily be a virus
what happen
oh
can sum1 dm me saying rate nd then go thru and tell me if theres anything i could do better
We generally discourage people moving to dms for this kind of thing.
It can get kinda sketchy
well can i send it here
How long is the presentation?
If it's not too long just taking screenshots might be viable.
The whole "download my file and check it" thing is also sorta sketchy
Idk if people are going to want to do that.
if this is going to be presented on a large screen, some of the text might be quite small. i didn't look at the content, but the presentation is quite sleek. also you censored your name page 1 but your full name is signed on each page
also this isn't really math feedback lmao
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I want help on Q6 of BMO1 2021, doing the olympiad on Wednesday
Haven't really got anywhere
so it's $(a_1+1)(a_2+1)\cdots(a_n+1)$ where $\sum a_i = 70$
Dreyuk
36+12+10+6+2+2+2 = 70 so it's just the number of ways to rearrange the factors of 999,999
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I am at a complete loss for trying to solve for k. I’ve tried setting the area of the triangle formed by g(x) equal to the integral the upper region plus the lower region to isolate k, and got k = 3, which makes zero sense in the context of this problem. I got the same result by trying the same method but with the trapezoidal shape. One of my buddies set up a system of equations and got k as 6.61, and another one got it as exactly 7. We are all at a loss.
show all your work
why are you calculating this area
oh are you calculating the area of the triangle connecting A to (k, 0) and (k, g(k))?
yea you can do that and then subtract the area under f(x) between 5 and k
you don't need an integral to find the area of a triangle
but you would for $\int_5^k \frac{1}{x-4} + 1 dx$. so evaluate that and then do the subtraction
riemann
@modest pagoda Has your question been resolved?
won’t that leave this or am i misinterpreting?
oh yes you have to subtract off another triangle
oh that gives you the unshaded region
the full triangle minus the integral you described gives the yellow region
yea it's probably just easier to find the small triangle with AB hypotenuse + the second integral i mentioned.
what is this supposed to be
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also why does your definite integral still have an x
left side is the full triangle, right side is the sum of the areas making up the triangle to make them equivalent
.reopen
✅
that's circular
typo, meant to be k. still canceled out in my work
after this, you set it equal to log(p) + 8
then solve for p
and set the non log stuff equal to 8
i cannot leave it in terms of k
this gives you k
or at least an equation for k
then you have 2 eqns 2 unknowns
why equal to 8?
why is the 8 the only part of that equation being used in the part you described
you see your log here right?
yes
that argument is equal to p
that’s where my disconnect was. thank you for your help
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if im given tangent on a unit circle, how do i find secant?
$\tan^2(x)=\sec^2(x)-1$
fish
you can then use the appropriate quadrant to figure out the sign
@raven swift Has your question been resolved?
suppose im giving tangent as -3/4
ik tangent is sin/cosine
and secant is 1/cos
so 1/4?
no. that would be assuming that sine is -3, which is outside the range of the function
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I'm doing line integrals this week, I know the basics of them, I'm just not sure how to set this one up.
What would the integral bounds and r(t) be?
@lone imp Has your question been resolved?
No
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ok
(4x²)^4?
thank you too
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How am I supposed to set this up?
Our teacher just gave us our first actual worksheet/packet on optimization and I feel kinda lost. I figured there was a relationship between the triangles (similar) and I can use that w/ pythagorean formula?
Work in terms of z^2, not z. Minimising z^2 is the same as minimising z.
I would start afresh on new paper from "x/(x+1) = 8/y". The form "(x+1)/x = y/8" is preferable, as you can simplify (x+1)/x to 1 + 1/x. Eliminate one of the variables in the pythagorean formula and minimise what you get
Have you done differentiation yet?
yes, we've covered differentiation
Just expand that, differentiate it, set it equal to zero and solve for x
gotcha; what was wrong w/ what I did then 😦
if you get multiple solutions check what values of z they give you and see which is smallest
let me read it
- respectfully, I would always try and work downwards rather than forcing yourself to stay on the same page. It's far far better to use more paper and make your work clearer
- Best to minimise z^2 rather than z. It's far better to think of it that way if you can see why - no confusing square roots lying around
i understand; I've ran out of paper though. I'll try to see if I have a sheet that's blank in the back somewhere
yeah I see what you mean
I'll give it a shot and see how far I get, thanks mate
before I dive head first into that, do you mind helping me with setting up this problem:
so what I did was I made a similar triangle relationship then I did all the math only to realize there's no max to the relationship I made
The way I would think about this is a circle centred on the corner
Chat GPT said something about making two similar triangles in the hallways and adding up their hypoteneous values to form the ladder, but when I tried that I got crit pt at x=0 but ig I could've done the math wrong
Don't use chatgpt for maths help, it's dumb
hmmmm. How does that work 🤔
yeah it was rly annoying
If you have the best ladder length, you'll put the ladder centre at the corner and rotate it about the centre. You want the arc traced out by the ladder edge (the arc of a circle) to fit inside the corridor
that may be wrong actually
yeah that's only correct when the hallways are the same width, ignore me
I barely understood enough to read 😭
wait, that's actually really really neat
def will use that if they r the same width
I don't think 5/7 = (5+y)/(7+x) is correct
Because as you move the ladder through, your triangle will dynamically change what angles it's at, you're rotating it
it's not
i tried doing it that way but the similar triangle relationship I'm making is always increasing (you can see the remnants of my work in the eraser marks)
yeah that's what GPT said it just went no where with it
ladder length = L
as you move the ladder, the lengths x and y change
but you'll have L^2 = (5+x)^2 + (7+y)^2 at all times
may be best to swap x and y actually, since x usually means horizontal distance
the x's and y's in pencil, right?
What do you mean?
red x and blue y r constant
i could be mis-interpreting keep that in mind
but if you were to move the ladder
not constant
why not
oh wait
i see
cuz the ladder moving is the hypotenous
this only holds if your ladder is touching against both walls
if x=0, your ladder is horizontal. It can't touch both the corner and the bottom line.
yeah
yeah
it's a thinker
and then your similarity constraint is 5/y = x/7
So, "maximise (5+x)^2 + (7+y)^2 with constraint 5/y = x/7"
where'd u get this constraint
Can you see from that diagram that they're similar triangles?
the two similar triangles?
that I do not get

