#help-27

1 messages · Page 270 of 1

errant sparrow
#

wdym add a constant?

topaz beacon
#

for example if you get f(1) = -4, what do you add to get 2?

errant sparrow
#

-2?

topaz beacon
#

-4+_=2

errant sparrow
#

6?

topaz beacon
#

yes

#

that is the constant you add

errant sparrow
#

for the second term here i get 1/4=c and n=4?

topaz beacon
#

dont forget about the negative sign

errant sparrow
#

so its -1/4?

topaz beacon
#

c = -1/4

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yeah

errant sparrow
#

so my equation shouldve been -x^3 = cnx^n-1 ?

topaz beacon
#

yeah

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or you could remember that there is a minus sign

errant sparrow
#

the last term is just x?

topaz beacon
#

but i prefer keeping the minus sign to not forget

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yes, the last term is just x

errant sparrow
#

i got
f(x) = (1/2) x^2 - (1/4) x^4 +x

topaz beacon
#

right, but we also have a really important +C

errant sparrow
#

wdym +c?

#

i just add +c to the equation and then sub in f(1)=2?

topaz beacon
#

remember how 3x+5 and 3x+7 have the same derivative?

errant sparrow
#

yes

topaz beacon
#

we need a function value to find what C is

#

plug the value in and solve for C

errant sparrow
#

so my equation is
f(x) = (1/2) x^2 - (1/4) x^4 +x +c
then i sub in f(1)=2?

topaz beacon
#

yes

#

many people forget the +C when doing antiderivatives

errant sparrow
#

for this one theres they give me two to plug in
do i do that the same way?

topaz beacon
#

notice that you have f''

#

you have to be a little careful with this one

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first we find f' by finding the function that has the derivative equal to f''

#

what function has a derivative e^x

errant sparrow
#

part A i got
f(x)= (1/2)x^2 - (1/4)x^4 +x +3
c=3?

errant sparrow
topaz beacon
#

yes

topaz beacon
errant sparrow
#

-3

topaz beacon
#

still doesnt sound right

#

how did you get that?

errant sparrow
topaz beacon
#

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-...

errant sparrow
topaz beacon
#

thats better

errant sparrow
#

f(x)= (1/2)x^2 - (1/4)x^4 +x +(3/4)
thats my final equation?

topaz beacon
#

yup

errant sparrow
#

this one i got
f(x) = x + 2x^(3/2) +c
and then i solve for c?

topaz beacon
#

yup

errant sparrow
#

the second term is ok ?

topaz beacon
#

yup

#

you can check by doing power rule

errant sparrow
#

yes it looks correct

#

f(x) = x + 2x^(3/2) +5
i get c=5?

topaz beacon
#

looks right

errant sparrow
#

and then for the last one , is f'' the same way to solve?

topaz beacon
#

you have to be a little careful

#

get to f', then ill show you what to do

errant sparrow
#

i have to do it twice?

topaz beacon
#

yes

errant sparrow
#

the -2sinx do i have to use the product rule?

#

or can it just be 2cosX

topaz beacon
#

just 2cosx

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you only need to worry about product rule if the two factors are both functions

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if one is a constant, you dont need to worry

errant sparrow
#

f'(x) = e^x - 2cosX

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?

topaz beacon
#

dont forget the +C

errant sparrow
#

i dont have to solve for f(x) first before i do the +c?

topaz beacon
#

but i want you to write it as $C_1$

woven radishBOT
#

me when the gbf

topaz beacon
#

you dont know f(x), so you cant solve for C

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C1, i should say

errant sparrow
#

so i sub it in twice with f(0) for c1 and then f(pi/2) for x2?

topaz beacon
#

not yet

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first off i want you to be careful with the -2sinx part

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derivative of cosx = -sinx, so the minus sign turns into a plus sign

errant sparrow
#

so it would be +2cosx?

topaz beacon
#

yes

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so our f' is e^x+2cosx+C1

errant sparrow
#

and then i sub in f(0)=3?

topaz beacon
#

no not yet

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we have our f', we need f

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can you find the first two terms of f?

errant sparrow
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f(x)= e^x -2sinx

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the c1 becomes a 0?

topaz beacon
#

we are working backwards, so the derivative of what becomes a constant?

errant sparrow
#

wdym?

topaz beacon
#

using the reverse power rule method or any other method, the derivative of what becomes C1?

errant sparrow
#

cx?

topaz beacon
#

yeah C1*x

errant sparrow
#

f(x)= e^x -2sinx +c1x ?

topaz beacon
#

watch your signs on the trig function again

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derivative of what function becomes +cosx? is it +sinx or -sinx?

errant sparrow
#

+2sinx

topaz beacon
#

yes

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so our function is f(x) = e^x+2sinx+C1*x, but we are msising something

errant sparrow
#

another constant?

topaz beacon
#

yes

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C2

errant sparrow
#

we add c2 to the end of that equation?

topaz beacon
#

yup

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then you can plug in your function values to get a system of equations to solve for C1 and C2

errant sparrow
#

one at a time?>

topaz beacon
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plug in x=0 first

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this will get rid of C1, because C1*x = C1*0 = 0

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no system of equations needed

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just some algebra

errant sparrow
#

c2=2?

topaz beacon
#

yup

errant sparrow
#

f(x)=e^x +2sinx +c1x + 2

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how did i know to plug in f(0) =3 first?

topaz beacon
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because it gets rid of the c1x term

errant sparrow
#

would it be wrong if i pluged in f(pi/2)=0?

topaz beacon
#

if you plugged in pi/2, then both variables are there and you cant solve anything

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i should say unknown constants, not variables

errant sparrow
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do i always plug in the first one or i have to know which one to plug in?

topaz beacon
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you could plug in either first, and then youll find out which one is more useful

errant sparrow
#

got it

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so now i have to find c1?

topaz beacon
#

you may find both are not too useful, but together they form a system of equations to solve them

topaz beacon
errant sparrow
#

i plug in the f(pi/2)?

topaz beacon
#

yeah, plug in x= pi/2

errant sparrow
#

How would I solve this?

topaz beacon
#

you can leave it in exact form or approximate it by plugging it into a calculator

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it has no clean answer

errant sparrow
#

I got this?

topaz beacon
#

,calc (-e^(pi/2)-4)/(pi/2)

woven radishBOT
#

Result:

-5.6089241047199
topaz beacon
#

looks right

errant sparrow
#

my final equation
f(x) = e^x + 2sinx -5.61x +2

topaz beacon
#

looks good

errant sparrow
#

ok thats the last question

#

tysm for ur help

topaz beacon
#

youre welcome

errant sparrow
#

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restive river
#

simple question, for part c what does it mean by initial depth?

restive river
#

Would that be 0?

#

oh ok got it

#

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eager cliff
#

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?

eager cliff
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Just wondering if I’ve gone wrong here

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Since the answer is irrational

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<@&286206848099549185>

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<@&286206848099549185>

opal cloak
#

all caps when you spell the mans name

eager cliff
#

Is my Spotify status still visible?

opal cloak
#

no

eager cliff
#

Oh

opal cloak
#

ur name is a dead giveaway

eager cliff
#

Yeah

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So just checking I haven’t done a step wrong

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I feel like I have but I can’t tell why

woven radishBOT
opal cloak
#

the ratio between the sides and their areas arent the same i believe

eager cliff
#

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

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Well if the ratio is 36:121

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And the smaller side is 15cm

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Wouldn’t it make sense to cross multiply

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?

opal cloak
#

the answer being irrational shouldnt be a problem

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just let me check something

eager cliff
#

K

opal cloak
#

is the question assuming that they have the same heights?

eager cliff
#

Well that’s all the info given in the question

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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

opal cloak
#

thats not what im asking

eager cliff
#

Oh

opal cloak
#

the height of the smaller rectangle is 2.4cm so are we assuming that is also the height of the larger rectangle?

eager cliff
#

There’s no given height?

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And the heights of the two rectangles would correlate to the ratio 36:121

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Wait I just realised

opal cloak
#

yeah but thats my problem, the areas are in a ratio

eager cliff
#

Areas

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Oh my days I need to square root it

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Ok I’m all good

opal cloak
#

uhh ok

eager cliff
#

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stray ravine
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stray ravine
#

im not sure about how i would start question D

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rancid pelican
#

this is rational function and i am not sure about the graph im just posting here just to check the graph

past bough
#

not quite

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look at values close to -1 and see what happens

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and you're y-axis isn't consistent

glossy dew
#

meaning having the same difference

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for a normal graph the difference in nearby markings would be same

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you would get a function like this if plotted properly

rancid pelican
#

okok i see

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thanks as always

glossy dew
#

just one more thing

rancid pelican
#

yeah wahts up

glossy dew
#

maybe try marking the graph with y axis marked as -1, -0.5, 0, 0.5, 1... and then drawing the graph

rancid pelican
#

gotcha gotcha im noting all this down

#

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vast quiver
#

Let the family set Ai with i ∈ N ∶ Ai =] - ∞, i]. Show that ∩i∈N Ai = ⋯

vast quiver
#

is ∩i∈N Ai = (-inf,0]?

winter torrent
#

seems right to me

#

assuming 0 is a natural number

vast quiver
#

yeah

#

and are there any problems while trying to prove it?

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Is this fine

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@vast quiver Has your question been resolved?

vast quiver
#

@winter torrent

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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radiant rune
#

how do i solve these two quesitons?

devout snowBOT
radiant rune
#

im confused

hushed wraith
#

f is a simple enuf function

#

I think u can sketch what the integral of that looks like

coral violet
#

do you know the libenez theorem

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i think that’s what its called..

radiant rune
#

0_0

coral violet
#

Ill give you the proof, hold on..

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somber shore
#

hi

devout snowBOT
somber shore
#

could you please give me a hint for this

#

here is how far i could go

#

btw

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i made a mistake

strong tiger
#

why did you substitue x = 1 - e^4

somber shore
#

e^ u

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bad handwriting sully

strong tiger
#

you should follow a rule

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that substitute a function whose derivative is present

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try again using that again

somber shore
#

i tried that but nothing came to my mind

#

1/x is deriv of ln (x)

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the only thing that might work is this ig

strong tiger
#

do you know what is the derivative of ln(1+x)

somber shore
#

1/(x+1)

strong tiger
#

oh wait

#

ah damn im dumb

somber shore
#

all good

strong tiger
#

sorry

somber shore
#

the ln on the top

#

is so annoying

snow raptor
#

you can use series

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ln(1-x)

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find the series of that

strong tiger
#

uhh

#

listen

somber shore
strong tiger
#

try ln(1-x) = u

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that will work maybe

snow raptor
#

I'm not sure

#

bc this can be expressed into special integral of log

strong tiger
#

huh

snow raptor
#

Li(x)

strong tiger
#

im getting something

#

lemme cook

snow raptor
#

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...

somber shore
snow raptor
#

I don't know which sub to take but I only know using series

strong tiger
#

😭 i tried

#

i got the same integral again

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wasted yall time sorry

somber shore
somber shore
snow raptor
#

to match that form

somber shore
snow raptor
#

multiply by -1

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I will show you wait

#

$-\int(-\frac{ln(1-x)}{x})$

woven radishBOT
#

Alaska

somber shore
#

ok ok

snow raptor
#

so its -Li_2 (x)

#

I don't really know how to evaluate limits

#

this is higher math

somber shore
#

tysm then i should wait till i understand series

#

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gloomy moat
#

How can I quickly tell if this matrix has independent columns?

gloomy moat
#

and how can i see which columns are not independent?

acoustic leaf
#

consider whether 4 vectors in R^3 can be linearly independent, generally

gloomy moat
acoustic leaf
#

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

gloomy moat
#

hm okay thx

#

do you know how i could do the "The Strang Decomposition A = CR" on this?

acoustic leaf
#

i believe you start by taking the RREF of the matrix in question

gloomy moat
#

idk i never heard of this

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RREF

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i prob wont have enough time to do all these steps anyway in the exam lol

#

there has to be a trick

acoustic leaf
#

you haven't heard of reduced row echelon form?

gloomy moat
#

this ?

acoustic leaf
#

yes

gloomy moat
#

yeah im confident u can do this without using RREF

#

the prof also said that we wont have time to do calculations

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so yeah

acoustic leaf
#

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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plucky maple
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plucky maple
#

Do they mean probability of 1st success of 7 MORE trials after the 5 failed trials(same for 2?)?

faint zinc
#

No, 2 more trials for a total of 7.

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plucky maple
#

Wait lemme process

plucky maple
#

Of course yeah that makes sense

#

Ty so much

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covert umbra
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covert umbra
#

!status

devout snowBOT
#
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
covert umbra
#

1......

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#

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faint gorge
# covert umbra

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 ]

woven radishBOT
#

𝔸dωn𝓲²s

covert umbra
#

what does My mean

faint gorge
#

partial derivative wrt y

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mossy rapids
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mossy rapids
#

i solved and got 2 for the value of k

#

now orthocentre is equidistant from all the vertices

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so i took ortho centre as (x', y') and did using distance method

#

but unable to get the ans using that

uncut imp
#

Maybe just compute where 2 altitudes intersect?

mossy rapids
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marble otter
#

Hello!
I have the following "table" and want to calculate this:

marble otter
#

I know that the solution would be this:
I don´t know where to start blobsweat

upper schooner
#

Do you have any additional context?

marble otter
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warped prism
#

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.

woven radishBOT
#

ZaoWuZhu

warped prism
#

Broke it into the dyadic partitions, but struggle to see what to do after

random helm
# woven radish **ZaoWuZhu**

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.

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#

@warped prism Has your question been resolved?

warped prism
#

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}}.
]

woven radishBOT
#

ZaoWuZhu

warped prism
#

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}}.
]

woven radishBOT
#

ZaoWuZhu

magic wind
#

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.

warped prism
#

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,

woven radishBOT
#

ZaoWuZhu

warped prism
#

I tried to flesh it out a bit

magic wind
#

Looks good.

warped prism
#

appreciate man 🙂

#

that hint really helped out

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lapis sparrow
#

I feel like I have an idea of where to start; however, I would like some assistance

lapis sparrow
#

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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green vortex
#

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

green vortex
#

nevermind, the teacher made an error it was +1

#

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wind root
#

Hallo I need an explanation why these are the formula when finding FV and PV in compound interest.

wind root
#

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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prime whale
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prime whale
#

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

acoustic leaf
#

the negative should still be there

#

if you flip the mu vector that changes the angle

prime whale
#

so instead of |a||b| cos its

#

-|a||b| cos

#

?

acoustic leaf
#

yes

#

alternatively you can bring the - inside the cos as a change to the angle

prime whale
#

hmm ok

#

thank you

#

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unreal lynx
#

what is the technique called that allows you to do this kind of math by hand without a calculator? 11^5 mod 13

unreal lynx
#

that's great but how does that answer the question?

faint gorge
#

there is no techniuqe

#

it's just logic and knowing some modular arithmetic

unreal lynx
#

I think it might be "square and multiply" @faint gorge

fossil locust
#

there's also Hensel's lifting lemma if you are interested

unreal lynx
#

I am interested in the simplest and quickest solution

#

which with a name like that I think I will stick to the first

fossil locust
#

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

unreal lynx
#

thanks

fossil locust
#

no worries!

unreal lynx
#

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proven grove
#

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

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#

@proven grove Has your question been resolved?

proven grove
#

<@&286206848099549185>

dense badge
#

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

proven grove
#

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

devout snowBOT
#

@proven grove Has your question been resolved?

charred zodiac
devout snowBOT
#

@proven grove Has your question been resolved?

proven grove
#

but the answer key says that there are none inflection points that are also extrema

#

here is the graph in desmos

charred zodiac
charred zodiac
proven grove
#

also it’s a no calc problem i wasn’t even supposed to be graphing it

proven grove
#

it changes from concave down to up

charred zodiac
#

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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rancid spire
#

Hey! How to multiply

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stone stump
#

how to multiply what

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fierce matrix
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upbeat pawn
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upbeat pawn
#

why does labda become 1

fringe meadow
#

like what does it actually mean

upbeat pawn
#

the scalar right

fringe meadow
#

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?

upbeat pawn
#

ya

fringe meadow
#

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?

upbeat pawn
#

uh not rly

#

why dont they write lambda in the first place

#

Ax= lambda x

#

i understand this much

fringe meadow
#

Because it says the number of visitors is constant, so if lambda was there it would mean that its not constant

upbeat pawn
#

and when lambda =1 it becomes Ax= x

fringe meadow
#

as every transformation would scale up or down the number of visitors

fringe meadow
upbeat pawn
#

no

fringe meadow
#

So what must the scalar be?

upbeat pawn
#

1

fringe meadow
#

There you go

upbeat pawn
#

wait

#

lemme slowly digest

fringe meadow
#

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?

upbeat pawn
#

only the total (kid , adult, elderly visitors) remain the same but the individual visitors of each category changes ?

fringe meadow
upbeat pawn
#

this part multiples with identity matrix to factorise [G I M]?

fringe meadow
upbeat pawn
#

ok thx

fringe meadow
#

All clear?

upbeat pawn
#

i kindda get the basic concept

#

this chapter is so ass

fringe meadow
#

watch 3b1bs essense of LA it clears up alot of stuff

fringe meadow
upbeat pawn
#

eigenvector and eigenvalues

fringe meadow
#

you take a levels by any chance?

upbeat pawn
#

this was the question

fringe meadow
upbeat pawn
#

but without further maths

fringe meadow
#

Then why you doing this, its FP2?

upbeat pawn
#

im in uni

fringe meadow
upbeat pawn
#

egineering maths shi

fringe meadow
#

you had a pre uni maths

#

role

upbeat pawn
#

so this chap is basically new to me

#

college math basically

#

only standard a level maths

#

not the further maths

fringe meadow
upbeat pawn
#

youtue?

fringe meadow
#

would highly highly recommend

fringe meadow
#

what uni you in?

#

if you dont mind sharing

upbeat pawn
#

monash

#

wbu

fringe meadow
#

Im in y12

upbeat pawn
#

h

#

oh

fringe meadow
#

still got a while

upbeat pawn
#

college at?

fringe meadow
#

Eyeing trinity maths

upbeat pawn
#

u took further maths?

fringe meadow
#

Im taking right now

upbeat pawn
#

oh nice

fringe meadow
#

Exam is next year

upbeat pawn
#

i dropped it after a few months lmao

fringe meadow
#

I have to take it cause I wanna study maths 💀

#

but our school picked further stat and mech

#

which I hate

upbeat pawn
#

well if u like maths den go ahead

fringe meadow
#

hate hate hate

#

mechanics is just yuck

upbeat pawn
#

thats the requirement for everyone who took fm

#

¯_(ツ)_/¯

fringe meadow
#

No its optional in FM

upbeat pawn
#

huh

fringe meadow
#

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

upbeat pawn
#

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?

fringe meadow
#

We re doing AS topics rn in school but Im doing A2

upbeat pawn
#

smart guy

#

prodigy type shi

fringe meadow
#

below average for cambridge applicants

#

lol

upbeat pawn
#

thats a high aim

fringe meadow
#

they did this in primary

upbeat pawn
#

nah

#

no way

fringe meadow
#

Im obviously joking but they're still really cracked

#

anyways i gotta get some work done

#

good luck with your eigenvalues and vectors chapter

upbeat pawn
#

kk thx for help

#

bye

fringe meadow
#

cya

upbeat pawn
#

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restive river
#

Can some pls explain example 38.1

I want the example explaines not the exercise

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restive river
#

Can anyone pls explain example 38.1 pls

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restive river
#

<@&286206848099549185>

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left palm
#

you have two right triangles and they're congruent by hypotenuse-leg

restive river
#

Oki

left palm
#

then you compare congruent parts

#

that should be it

restive river
#

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

left palm
#

well that perpendicular part gives you the right triangles

restive river
#

I get that AB is a chord
OA and OB are the same length

But OBA

left palm
#

the chord bisection doesn't matter so much since they told you it's the midpoint already

#

what about OAB?

restive river
#

Sorry OBA

left palm
#

right, we have to right triangles

restive river
#

How is OAB and AOB same

left palm
#

they share the hypotenuse (radii) and a leg (OX)

restive river
left palm
#

there's a hypotenuse-leg theorem for right triangles which says they're congruent

restive river
#

Ok

left palm
#

then you can use CPCTC (corresponding parts of congruent triangles are congruent)

restive river
#

Ok

left palm
#

that should be it

restive river
#

Ok.thank u very much.have a nice dayy

left palm
#

thanks you too!

restive river
#

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oblique mulch
#

I did the ratio test to find the convergence for this power series but I’m not really sure at this point?

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#

@oblique mulch Has your question been resolved?

faint gorge
#

also check end points

sage burrow
#

assume x = 2 and look what series you would get ...

oblique mulch
faint gorge
oblique mulch
#

so I should be taking the ratio test upside down with an above an+1?

faint gorge
#

either that or just consider the reciprocal as you see, a_n/a_(n+1)

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grim ginkgo
devout snowBOT
grim ginkgo
#

is the answer b =2?

#

thats what i got

#

if it isnt imma need some help cantlie

supple knot
grim ginkgo
#

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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blazing crest
#

3b anyone?

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#

@blazing crest Has your question been resolved?

supple knot
#

did you try proving it when I = [a, b]

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blazing crest
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cerulean wharf
#

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?

cerulean wharf
#

Is there any theorem or lemma about this?

#

Maybe leftover hash lemma 🤔

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@cerulean wharf Has your question been resolved?

cerulean wharf
#

Hmm B1 and B2 must be very close because the min entropy differs by an exponential 😔

cerulean wharf
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hexed holly
#

Have I done this right?

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hexed holly
#

i think i need to add b + a = RHS, but there's no answer so i'm not sure.

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rose ingot
#

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.

hexed holly
#

okay, thank you!

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north pivot
#

Hey ! Can anyone help with finding the ways to resolve the first integral ? I am kind of stuck

proud perch
#

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)

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north pivot
#

This is what I found

#

but when i write the integral down it seems unclear on the limits

proud perch
#

wdym

proud perch
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proud perch
#

.reopen

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slate rose
#

sure

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vale pawn
#

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

vale pawn
#

great i forgot how to use latex after years uh

#

i got a and b correct but i dont know why is this wrong

#

please enlighten me

#

thx

#

oh, nvm

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restive river
#

just want some confirmation on this

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restive river
#

I did evreything now for the helicopter off the ground

#

would I just do 661sin 28 degrees 11 and 445sin 44.5 degrees

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restive river
#

<@&286206848099549185>

atomic sparrow
#

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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hot hamlet
#

how do i solve this

devout snowBOT
hot hamlet
#

i need to draw something too

#

pls help\

supple knot
#

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

hot hamlet
supple knot
#

t is another variable

hot hamlet
#

ok and what about this:

supple knot
#

,tex .shift trig

woven radishBOT
#

riemann

supple knot
#

either top left or one beneathe it

hot hamlet
supple knot
#

why

hot hamlet
#

my teacher asks me various method, he might ask me to do another way

#

and the test is tomorrow

#

😭

hot hamlet
supple knot
#

go through your other trig identities then

#

i don't know what you learned

hot hamlet
#

alr

#

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sonic igloo
#

help

devout snowBOT
sonic igloo
#

can sum1 tell me if the power point is ok

cold bough
#

sus

sonic igloo
#

and be honest

cold bough
#

it could easily be a virus

sonic igloo
#

it could also easily real..

cold bough
#

though

sonic igloo
#

nope

#

computer sci

#

but i need sum1 to rate it

supple knot
#

wtf

#

<@&268886789983436800>

sonic igloo
#

oh

#

can sum1 dm me saying rate nd then go thru and tell me if theres anything i could do better

modest dagger
#

It can get kinda sketchy

sonic igloo
#

well can i send it here

modest dagger
#

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.

sonic igloo
#

ok

left palm
#

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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hollow jay
#

I want help on Q6 of BMO1 2021, doing the olympiad on Wednesday

hollow jay
#

Haven't really got anywhere

violet wind
#

so it's $(a_1+1)(a_2+1)\cdots(a_n+1)$ where $\sum a_i = 70$

woven radishBOT
#

Dreyuk

violet wind
#

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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modest pagoda
#

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.

supple knot
#

show all your work

modest pagoda
#

my friend’s system:

#

and i do not have access to the 3rd person’s work

supple knot
#

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

woven radishBOT
#

riemann

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#

@modest pagoda Has your question been resolved?

modest pagoda
supple knot
#

oh yes you have to subtract off another triangle

#

oh that gives you the unshaded region

modest pagoda
#

the full triangle minus the integral you described gives the yellow region

supple knot
#

yea it's probably just easier to find the small triangle with AB hypotenuse + the second integral i mentioned.

modest pagoda
#

setting all that up causes k to cancel out

supple knot
#

what is this supposed to be

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supple knot
#

also why does your definite integral still have an x

modest pagoda
#

left side is the full triangle, right side is the sum of the areas making up the triangle to make them equivalent

supple knot
#

.reopen

devout snowBOT
#

modest pagoda
supple knot
supple knot
#

then solve for p

#

and set the non log stuff equal to 8

modest pagoda
#

i cannot leave it in terms of k

supple knot
#

or at least an equation for k

#

then you have 2 eqns 2 unknowns

modest pagoda
#

why equal to 8?

supple knot
#

use the information given

modest pagoda
#

why is the 8 the only part of that equation being used in the part you described

supple knot
modest pagoda
#

yes

supple knot
#

that argument is equal to p

modest pagoda
#

that’s where my disconnect was. thank you for your help

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raven swift
#

if im given tangent on a unit circle, how do i find secant?

coral heron
#

$\tan^2(x)=\sec^2(x)-1$

woven radishBOT
acoustic leaf
#

you can then use the appropriate quadrant to figure out the sign

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#

@raven swift Has your question been resolved?

raven swift
#

ik tangent is sin/cosine

#

and secant is 1/cos

#

so 1/4?

coral heron
#

no. that would be assuming that sine is -3, which is outside the range of the function

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lone imp
#

I'm doing line integrals this week, I know the basics of them, I'm just not sure how to set this one up.

lone imp
#

What would the integral bounds and r(t) be?

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lone imp
#

No

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faint gorge
#

ok

misty crest
#

oh

#

it was 8x btw

#

you forgot the x

whole raven
#

yeah i realised, i just entered it again with the x and still got marked wrong 😭

faint gorge
misty crest
#

yea

#

that too

whole raven
#

oh right

#

thanks guys

faint gorge
#

thank you too

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old carbon
#

How am I supposed to set this up?

devout snowBOT
old carbon
#

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?

tame spear
#

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?

old carbon
tame spear
# tame spear

Just expand that, differentiate it, set it equal to zero and solve for x

old carbon
tame spear
#

if you get multiple solutions check what values of z they give you and see which is smallest

tame spear
#
  • 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
old carbon
old carbon
#

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

tame spear
# old carbon

The way I would think about this is a circle centred on the corner

old carbon
#

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

tame spear
#

Don't use chatgpt for maths help, it's dumb

old carbon
old carbon
tame spear
# old carbon hmmmm. How does that work 🤔

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

old carbon
#

I barely understood enough to read 😭

#

wait, that's actually really really neat

#

def will use that if they r the same width

tame spear
#

Because as you move the ladder through, your triangle will dynamically change what angles it's at, you're rotating it

old carbon
#

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)

tame spear
#

May be a good observation that these ones are similar

old carbon
#

yeah that's what GPT said it just went no where with it

tame spear
#

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

old carbon
tame spear
old carbon
#

red x and blue y r constant

#

i could be mis-interpreting keep that in mind

#

but if you were to move the ladder

tame spear
old carbon
#

it would reach a point where y=0, and another where x=0

#

pencil x and y

old carbon
#

oh wait

#

i see

#

cuz the ladder moving is the hypotenous

tame spear
#

if x=0, your ladder is horizontal. It can't touch both the corner and the bottom line.

tame spear
tame spear
#

and then your similarity constraint is 5/y = x/7

tame spear
old carbon
tame spear
old carbon
#

the two similar triangles?

tame spear
#

yeah

#

when you rotate the ladder to a different angle, they stay similar