#help-23

1 messages · Page 407 of 1

flat frigateBOT
hoary seal
#

ohhh, so were looking for the upper bound

fathom jewel
#

If you had now a sine term, good luck solving for x

hoary seal
#

and then isolate the upper bound only

fathom jewel
#

you isolate x in 1/(2x²)<eps

hoary seal
fathom jewel
#

yes sir

#

although the last line is wrong

flat frigateBOT
hoary seal
#

my last line is wrong why?

fathom jewel
#

You are not defining M to be x that's silly

#

The whole idea is M such that x > M

#

and M is that lower bound you just derived

#

in other words, you made a wrong assignment of variables

hoary seal
#

since the funct is cont

fathom jewel
#

which func is constant

hoary seal
#

g(x)?

fathom jewel
#

g(x) is not constant, it depends on x here obv

#

g(x)=1/(2x²) was an upper bound for |f(x)-L|

#

and M(eps) is a lower bound for x

hoary seal
#

but we used the upper bound to find for the lower bound?

fathom jewel
#

yes

hoary seal
#

we coudve used the lower bound as well

so -1/2x^2

#

and solved for M

fathom jewel
#

no

#

we are only interested in upper bounds

#

for |f(x)-L|

#

the whole idea is to show that |f(x)-L| becomes small enough, you can like zoom in and there will be still points inside that little window

#

working with a lower bound of |f(x)-L| doesn't yield anything useful, cause you cant control how small |f(x)-L| would get

hoary seal
#

so was that the answer

#

just solving for M was our goal

#

I think my prof wants to prove it

fathom jewel
#

That was scratch work

hoary seal
#

yeah

flat frigateBOT
fathom jewel
#

the good thing is the scratch work already tells you how to start now

hoary seal
#

yes

#

so choosing values

#

for M

#

and epsilon

fathom jewel
#

Only M

#

epsilon is something arbitrary

#

imagine it's something given from the outside and your M(eps) has to work with that eps everytime

hoary seal
#

so were not getting the value of epsilon

fathom jewel
#

that's what your proof is about

hoary seal
#

once we prove it

fathom jewel
#

once you prove it, you are saying, give me any eps>0, my M(eps) will handle it always

hoary seal
#

so once we prove it, we can see if it works by plugging in epsilon which will give the corresponding M

fathom jewel
#

you can do that yea

#

that's why we prove things in the first place

#

it guarantees results

hoary seal
fathom jewel
#

yes

hoary seal
#

isn’t it x>M

fathom jewel
hoary seal
#

Oh it’s the same thing

fathom jewel
#

yes

hoary seal
#

so first step is to prove x>M

#

howd o I do that

fathom jewel
#

blud

#

that is given

#

If x>M then ... is what you prove

#

You did the scratch work to find a suitable M

clever tinsel
#

you're not interested in the case where x < M anyway, if I may add.

fathom jewel
#

cause that's thankfully never the case with our M KEK

hoary seal
fathom jewel
#

You are skipping steps

#

If a new reader looks at this they will be like "how?" "what just happened?"

#

Let eps>0 was good adding that, introducing variables that you intend to use, so the reader isn't confused

#

From the def. is fine

#

Then you write a small sentence like choose M = bla such that x > bla

#

then you start with |f(x)-L| and show every step until you arrive at < eps

#

using x > bla

clever tinsel
#

do you think a template for this kind of proof would help?

fathom jewel
#

maybe but i wouldn't do that

clever tinsel
#

alright, sorry for interrupting.

fathom jewel
#

all g

#

I think the philosophy of letting someone fail and thus gain understanding is of more of value than handing them blindly a template to follow

clever tinsel
#

that is a fair point, sorry for not considering that.

fathom jewel
#

Cause a machine can also just follow blindly orders but it cannot analytically think and that is the actual skill you acquire doings math

clever tinsel
#

I agree. sorry once again; I'll step back.

fathom jewel
#

It's okay lol no need to be sorry, OP seems to be gone anyway

#

just an exchange of ideas DGloliDance

safe radishBOT
#

@hoary seal Has your question been resolved?

hoary seal
#

Oh I’m back

#

Let epsilon>0 and Choose M = some number > 0 such that |f(x)-L|<epsilon,
Then solve for epsilon once u sub values in
sin(x)/2(sqrt(1/2*epsilon)^2| < epsilon

clever tinsel
#

wait wait, so you're presumably using the Euro sign as epsilon, but then in your expression you have the word epsilon in it.

#

so is the Euro sign meant to be epsilon or some other variable?

fathom jewel
#

what the blud

hoary seal
#

Epsilon

clever tinsel
#

then what does the word epsilon itself mean in your expression in the last line?

fathom jewel
#

Let €>0 and Choose M = some number > 0 such that |f(x)-L|<€,
such that is wrong, that's what you want to show

hoary seal
#

Edited

fathom jewel
#

You choose M such that x>M cause this is what you will be using in your proof

hoary seal
#

Yes choosing a value greater than x

#

But we don’t know the value of M , it’s a general function

fathom jewel
#

Then solve for epsilon once u sub values in
sin(x)/2(sqrt(1/2*epsilon)^2| < epsilon
That's also terribly stated

#

You can't just plug in stuff, it's an inequality, not equation

flat frigateBOT
fathom jewel
#

This is how you structure the proof, and in the middle of inequalities you have to apply x>M

hoary seal
# flat frigate

Oh then we can plug in the function, limit and make it less than epsilon

#

Which we already have from our scratch

fathom jewel
#

yes and you are trying to show it's always less epsilon

#

yes

hoary seal
hoary seal
#

To solve for epsilon

fathom jewel
#

Two things: you dont write < epsilon out of nowhere, you derive that result

#

Second thing, you dont plug in M for x, you bound your expression using x>M, thus you inject epsilon automatically into the inequality and the math sorts itself out

hoary seal
#

Two confusions:

  1. how do we derive the result
  2. Bound your expressions using x>M? wdym?
fathom jewel
#

After you start with |f(x)-L| this is how you continue

#

If you are at this step we may continue

hoary seal
#

Underneath the line

fathom jewel
#

remove the < eps

#

this is your goal not your starting point

hoary seal
fathom jewel
# hoary seal

ok but here is the think how are |f(x)-L| and |sin(x)/(2x²)| related

#

just two expressions and you didnt derive them in your proof

hoary seal
#

so its all about connections

#

for proofs

fathom jewel
#

of course it is

#

else it's just a claim

#

a proof is just a chain of logical arguments that follow up

hoary seal
fathom jewel
#

here is the thing, you dont need to show how you got M

#

but in your actual proof, again you want to show |f(x)-L| < eps

#

so you start with |f(x)-L|

#

and from the scratch work you can see how to simplify this expression in the first place

#

so that we can apply x>M(eps)

#

and then your prove ends hopefully at < eps

#

îf you are stuck we can also do it together

#

in latex

hoary seal
#

so i would need to define whats f(x) and L

fathom jewel
#

no that's given

#

f(x)=(x²+sin(x))/x² and L=1/2

hoary seal
#

yes so do we write tht in our proof

fathom jewel
#

yes

#

then next step is to simplify it

fathom jewel
#

i also realized the =< were technically unnecessary but anyway

hoary seal
fathom jewel
#

because the scratch work is not a proper proof, you are working backwards

#

it would be circular since you assume what you want to prove in the first place is true

hoary seal
#

is proving when u need to go from finished product to the start product

fathom jewel
#

it's only for you to discover a possible M

#

no other way

#

but sometimes when we dont know how to start, we do backwards thinking in hopes of gaining something that might help

hoary seal
#

I see

fathom jewel
fathom jewel
#

then this is where things get interesting for the proof, but before that i want you to be ready

hoary seal
#

good so far?

fathom jewel
#

the "which simplifies" step is cocky, it's not trivial, in the exam you should really do the extra step with 1/2=x²/(2x²) but yes good so far, dont forget the =

hoary seal
#

do I find the upper bound now

fathom jewel
#

how can you bound |sin(x)|

hoary seal
#

I mean the same proccess from the scratch work

fathom jewel
#

which means

#

be concrete

#

write it mathematically

hoary seal
#

bound sinx by 1 and -1

fathom jewel
#

yes

#

so |sin(x)| =< ?

hoary seal
#

1

fathom jewel
#

yes

flat frigateBOT
fathom jewel
#

the chain of logical steps

#

but now comes the part that separates your scratch work from the real proof

#

from 1/x^2 we need to derive that it is smaller than eps

#

fortunately we have our assumption

#

so we know something about x and how to continue bounding it (thanks to our scratch work)

hoary seal
#

do we make thhis an equal sign

fathom jewel
#

we dont

hoary seal
#

from the previous step

fathom jewel
#

cause |sin(x)| is not always equal to 1

#

from the previous step it's immediate

#

x^2 cancels and we have |sin(x)| left and for the denom we can omit the abs values cause x^2 is always positive

flat frigateBOT
hoary seal
#

how did u get this. tho

fathom jewel
#

|sin(x)| is bounded from above by 1

#

at some point you cant forget that

hoary seal
#

but when u say |sin(x)| < 1

isnt that same as -1 < |sin(x)| < 1

fathom jewel
#

what

#

i mean

#

that's true but you dont need the lower bound

#

our focus is going up not down

hoary seal
#

if u put abs, it only looks for positive values

#

right

clever tinsel
#

at some point you have to remember the ultimate goal of what you're trying to do with these steps.
this is why Tairi at one point told you to write what you're given and what you are asked to do.

#

you cannot keep losing sight of the goal like this, OP.

fathom jewel
#

thanks Hanako Yukari

clever tinsel
#

kongouderp ?

fathom jewel
#

OH SRY

#

mb

#

bruh

clever tinsel
#

I would have thought Hanako would not be this cordial with this OP...

#

but either way, sorry for interrupting; please proceed.

fathom jewel
#

oh you know tairi

fathom jewel
#

we dont care at all about lower bounds right now

hoary seal
#

can u show me like a demo

fathom jewel
#

right now we are climbing up a mountain, so your focus is upwards not looking down

hoary seal
#

with another question

#

i want to see sample

fathom jewel
#

what sample what?

hoary seal
#

with another question

fathom jewel
#

we are about to enter the most crucial part and you are gonna forfeit lol

#

fine

hoary seal
#

im asking bc from the start of proof, my understanding is not there yet

fathom jewel
#

ok but then say that sooner not in the middle of something, especially that has been repeated for like 4 times now

ionic blaze
# hoary seal if u put abs, it only looks for positive values

that does not matter, in this case it's helping figure out the limit from the fundamentalz since it is squeeze theorem, we know that |sinx| is always non-negative AND is either less than or equal to 1/2x^2, as it approaches infinity, 1/2x^2 becomes zero, so logically, what's next

hoary seal
#

Ill come back to this question

#

.close

safe radishBOT
#
Channel closed

Closed by @hoary seal

Use .reopen if this was a mistake.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

forest osprey
safe radishBOT
forest osprey
#

What does chord refer to

#

Idk

#

Does it mean tangent at a point

#

Yo

arctic raven
#

I would've called it a secant line

peak estuary
#

in this case the points (x,f(x)) and (x+h, f(x+h))

timid ridge
arctic raven
#

it's like how chord is used in the context of circles also

forest osprey
#

Ook

#

So average gradient across that stretch

#

Hu

#

Its gradient at any point as well

forest osprey
broken forum
#

MenheraNo "average gradient across a stretch" sounds like you are taking a bunch of points between two boundaries and averaging the gradient. It is simply just the gradient line between two points

forest osprey
#

Ok .close

#

.close uhh

safe radishBOT
#
Channel closed

Closed by @forest osprey

Use .reopen if this was a mistake.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

shrewd frost
safe radishBOT
stoic dune
#

Did they forget a ... in that sum?

shrewd frost
#

Yess

stoic dune
#

Because if so, I think rationalising the denominator of each term could go pretty hard

shrewd frost
#

Yess this is the general term but what can i do next

primal gazelle
#

Each term is $a_k = \frac{1}{\sqrt{4k-3} + \sqrt{4k-1}} $

shrewd frost
#

I tried telescoping series

primal gazelle
#

do what kaynex said

primal gazelle
shrewd frost
#

But terms are not cancelling

primal gazelle
#

!show

safe radishBOT
#

Show your work, and if possible, explain where you are stuck.

timid ridge
#

u just need to know what it's around

shrewd frost
timid ridge
#

ok cool

plucky elk
#

,rotate

timid ridge
#

so it's going to be something like
1/2 * (sqrt(n + 2) - sqrt(n))

stoic dune
#

It's almost telescoping. It's like you're missing half the terms you need

shrewd frost
#

Yess

cunning pasture
#

Is it multiple choice?

shrewd frost
flat frigateBOT
cunning pasture
#

Single answer out of the four options?

shrewd frost
#

Yess

timid ridge
#

that's multiple choice

shrewd frost
cunning pasture
#

So single answer?

shrewd frost
#

Yesssss

cunning pasture
#

Then S > 24 cannot be the answer, because then S > 18 would also have to be true.
S < 24 cannot be the answer, because one of S > 18 and S < 18 must also be true.

Now we just decide between C and D.

shrewd frost
#

Yess

#

The answer given is B

#

Maybe something is incorrect

cunning pasture
#

If B is correct, C must also be correct.

shrewd frost
#

Do you know how to solve this

shrewd frost
cunning pasture
#

Perhaps we have the choose the tighest inequality.

shrewd frost
#

How can i do that??

rugged arch
cunning pasture
#

Anyway, is it intended to be done using calculus?

shrewd frost
#

No idea i have not tried that thing

cunning pasture
#

Do you know calculus?

shrewd frost
#

A little bit

cunning pasture
#

ok

#

because I don't

shrewd frost
#

It will be so much bad

#

Thia question should have a other easy way

#

@cunning pasture any idea bro how to approach this question?

#

<@&286206848099549185>

near sky
#

hi

cunning pasture
#

Hi Prof.

compact flame
#

after a bit of work

#

i come to

#

$$
S = \sum_{i = 1}^{4999} \frac{\sqrt{2i-1}}{\sqrt{2i+1}} - 4999
$$

flat frigateBOT
compact flame
#

oh wait im wrong

shrewd frost
#

How did you do this? @compact flame

compact flame
near sky
compact flame
#

try doing smth with the "missing series"

#

like 1/sqrt(3) + sqrt(5) + 1 /sqrt(7) + sqrt(9)

#

maybe a combined analysis of this with the series above yields a solution

compact flame
cunning pasture
#

Maybe this sum can be compared to a telescoping series which is smaller than this sum.

#

Because root(10000)/4 = 25

#

And WA gives its value > 25.

near sky
cunning pasture
#

Maybe use that 1/root(x) > 2(root(x) - root(x-1)).

safe radishBOT
#

@shrewd frost Has your question been resolved?

shrewd frost
#

Gimme a small example please

#

I am getting confused

cunning pasture
#

Ok, I know a solution (searched).
By the last inequality,
1/(4root(x)) > (root(x) - root(x-1))/2
|| 1/(2root(4x)) > (root(x) - root(x-1))/2||
||Take x = m + 1||
1/(2root(4m + 4) > (root(x) - root(x-1))/2
|| 1/(2root(4m+3)) > 1/(2root(4m+4) > (root(x) - root(x-1))/2 ||
So 1/(root(4m+3) + root(4m+3)) > (root(x) - root(x-1))/2
||1/(root(4m+1) + root(4m+3)) > 1/(root(4m+3) + root(4m+3)) > (root(x) - root(x-1))/2||
1/(root(4m+1) + root(4m+3)) > (root(x) - root(x-1))/2
||Now take the sum of both the expressions from m = 0 to m = 2499 or x = 1 to x = 2500||
||We get S > 1/2((root(1) - root(0) + root(2) - root(1) + root(3) - root(2) + ...... + root(2500) - root(2499)) = 1/2(root(2500) - root(0) = 1/2(50) = 25||
So S > 25

near sky
#

denote your sequence with A
general term of A $a_{k} =\frac 1 {\sqrt {4k -1}+ \sqrt{4k -3}} = \sqrt{4k-1} - \sqrt{4k -3}$

now define a new sequence for the missing terms \

$b_{k} = \frac1 {\sqrt{4k-1} + \sqrt{4k+1}} =\frac{\sqrt{4k+1} - \sqrt{4k-1}}2$

now compare kth terms of both you will find $a_{k}> b_{k}$

flat frigateBOT
#

professor paradox

safe radishBOT
#

@shrewd frost Has your question been resolved?

shrewd frost
#

Thank you so muchh @near sky @cunning pasture

safe radishBOT
#
Channel closed

Closed by @shrewd frost

Use .reopen if this was a mistake.

#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

mossy ridge
#

to guess a random number and being told higher or lower each turn the number is from 1-10000, whats the expected number of guesses to end game at picking randomly but still following higher lower criteria

stoic saddle
#

the best strategy is binary search

mossy ridge
stoic saddle
#

oh ok

mossy ridge
#

Whilst still following if they are being told its higher

#

So theyll pick a higher random number

radiant ice
#

cuz isn’t the answer just halving the higher/lower etc

mossy ridge
#

like can i give an example

radiant ice
#

sure

mossy ridge
#

say i choose say 2000

#

so you say 1354(random gueess from range 1-10000)

#

I say higher

#

You go 9456(random higher guess)

#

I say lower

#

You go 2679(random guess but it lies between 1354-9456)

#

Like this

#

How many turns is it expected before you get to the number

radiant ice
#

well i can be (n-1) since it’s random

#

for example

take i say the number 10,000

#

then you guess 1

#

then 2

#

then 3

#

….

#

9,999

#

10,000

mossy ridge
#

Thats not random tho

stoic saddle
#

it may depend on what the number is. like a number at an extreme can probably be guessed in a random no. of guesses faster than a number around the middle

mossy ridge
#

I mean that can happen but very unrealistically

radiant ice
#

i’m just saying like

#

n-1

mossy ridge
radiant ice
#

try with a smaller number

#

1-5

#

oh wait it is just N guesses

#

that’s the most probable

mossy ridge
#

I mean in N guesses youre sure to get it

#

It says expected

#

Like as in most probable number of guesses

radiant ice
#

yes

stoic saddle
#

please excuse me if im wrong

stoic saddle
#

this should be the case that E_n = 1 + 1/n + 1/(n(n-1)) + 1/(n(n-1)(n-2)) + ... + 1/n!

#

maybe not

mossy ridge
#

Like ur picking one and throwing it away

#

Each miss eliminates a lot of numbers each turn

stoic saddle
#

interestingly

#

E_n = H_n

#

where H_n is the harmonic sum

stoic saddle
stoic saddle
#

i mean in terms of a nice formula

mossy ridge
#

I mean yeah that formula is pretty funny

#

I mean why do i even have to do ts in cs

#

Ts pmo gng

#

Oh damn theres a formula for this

stoic saddle
#

so it is connected

mossy ridge
#

Yeah it definitelt looked like so

stoic saddle
#

wait it doesnt depend on the correct number?

#

or is it averaged over all designated correct numbers

mossy ridge
#

Apparently it doesnt

#

Its the overall expected value when youre also picking a random number

#

From the interval

stoic saddle
#

now prove it lol

mossy ridge
#

AW HELL NA

#

😭

#

I leave ts to the math nerd

stoic saddle
mossy ridge
#

Man how were humans smart enough to do all this

#

Ugh

stoic saddle
#

its very cool

mossy ridge
#

oh sorry for the smurf 😄

stoic saddle
#

damn

mossy ridge
#

I got into uni 2 years ago i should change it

stoic saddle
mossy ridge
#

Haha true that

safe radishBOT
#

@mossy ridge Has your question been resolved?

safe radishBOT
#
Channel closed

Closed due to timeout

Use .reopen if this was a mistake.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

fervent forum
#

Hi, I have an exam tomorrow but I needed help with a question on the continued proportion lesson

fervent forum
#

What happened in the third step here? What property exactly was used and how did it change it to that?

flat frigateBOT
plucky elk
fervent forum
#

What happened here?

plucky elk
#

do you have a table of properties of proportion in your book

fervent forum
plucky elk
#

show the formulas for all of them

plucky elk
#

yea property 3

fervent forum
#

The application? (K)

plucky elk
fervent forum
#

But it wasn't even used.

fervent forum
plucky elk
#

yea it was here

fervent forum
#

Huh?

plucky elk
#

why do you need a k in the solution

#

you're already told they're in proportion

fervent forum
plucky elk
fervent forum
#

Oh, but where did the y over 4 come from?

plucky elk
#

if A = B and A = C then B = C

#

i'll use capital letters to distuinguish from property 3

fervent forum
#

I don't get it...

plucky elk
plucky elk
plucky elk
fervent forum
#

I still don't understand where did the 4 over y come from

plucky elk
fervent forum
#

We replaced the k with it?

plucky elk
plucky elk
fervent forum
#

I mean y over 4 sorry

plucky elk
fervent forum
plucky elk
#

maybe your book calls transative something else

fervent forum
#

But what does it have to do with that?

plucky elk
plucky elk
plucky elk
plucky elk
fervent forum
#

OH WAIT
"= one of ratios"
y over 4 is a ratio so we replaced k with it?

#

It's because the sum of the anticedents over the sum of consequents would equal one of ratios and y over 4 is already one of the ratios

#

?

plucky elk
fervent forum
#

I feel so dumb lol 😭💔

#

Thank you for helping me tho

plucky elk
fervent forum
#

?

plucky elk
# plucky elk

being in proportion has a very specific meaning you should remember. not just y over 4 is a fraction

plucky elk
fervent forum
#

.close

safe radishBOT
#
Channel closed

Closed by @fervent forum

Use .reopen if this was a mistake.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

midnight steeple
#

I mean technically this is undefined right

midnight steeple
#

$Cov(X,a) &= E(Xa)-E(X)E(a) \ &= aE(X)-aE(X)\ &= 0$

flat frigateBOT
#

astral
Compile Error! Click the errors reaction for more information.
(You may edit your message to recompile.)

midnight steeple
#

$Corr(X,a)=\frac{Cov(X,a)}{\sqrt{(VarX)(Var,a)}} = 0$

flat frigateBOT
#

astral

midnight steeple
#

And Var(a) = 0

#

I don't think there's any other way to do it?

opaque berry
#

sm1 help with my statistics

frozen veldt
#

I mean certainly they can't be correlated (because the correlation coefficient is not defined) so therefore one could say they're uncorrelated

midnight steeple
#

lmao cool

#

.close

safe radishBOT
#
Channel closed

Closed by @midnight steeple

Use .reopen if this was a mistake.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

safe radishBOT
#

Please don't occupy multiple help channels.

#
Channel closed

Channel closed due to the original message being deleted.
If you did not intend to do this, please open a new help channel,
as this action is irreversible, and this channel may abruptly lock.

#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

solar inlet
#

Can any1 draw components in here as i cant figure it out

hard crest
#

start with the 6 N one, it'll be like 6 sin alpha north and 6 cos alpha to the right

the 5N one is similar, use the fact that it's alphaº from south (or 90º - alphaº from the right)

safe radishBOT
#

@solar inlet Has your question been resolved?

solar inlet
#

Tysmm

safe radishBOT
#
Channel closed

Closed by @solar inlet

Use .reopen if this was a mistake.

#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

white pebble
#

guys whats an easy way to figure out what the range of an function is?
for example 2x^(2) + 3x + 1

white pebble
#

i know theres an way with the vertex form

dull sequoia
#

for a quadratic you can find the vertex and direction of the parabola

white pebble
#

but idk

#

is the vertex an extrempoint?

dull sequoia
#

yeah

#

a min or max depending on the direction of the parabola

fathom jewel
#

Servus

white pebble
#

is the direction upward open for my example because it is 2x^2 and not -2x^2?

#

yo

#

nvm

#

how do i convert it to the vertex form, i am stuck idk what now

dull sequoia
white pebble
#

wym by that

dull sequoia
#

completing the square is how you derive the quadratic formula

#

have you seen the quadratic formula before?

white pebble
#

i am not sure

#

maybe

dull sequoia
#

i'd say go google or look at your textbook for the completing the square section

fathom jewel
#

Brauchst du Help

dull sequoia
#

yes i do

white pebble
#

tf

dull sequoia
#

that's the quadratic formula

white pebble
#

bruh

flat frigateBOT
white pebble
#

is there no easier way to figure out the range

#

i dont wanna remember an weird formula

dull sequoia
#

it's not a very weird formula

fathom jewel
dull sequoia
#

the trick is to remember how to get to the formula, not the formula directly (although many people are able to remember the formula because it is used often)

fathom jewel
#

for range

white pebble
#

the thing is that its just not worth it to remember just for the range

fathom jewel
#

frosst knows their stuff

white pebble
#

thats like 0.1% of the examen

dull sequoia
#

if you're only trying to pass the exam you've got the wrong attitude to learning :/

white pebble
#

i mean i wanna get an good grade

dull sequoia
#

there are many occasions when one wants to know this

#

if you study calculus, in integration you will again meet completing the square again

#

quadratics is quite the backbone to a lot of maths, it will show up all the time

white pebble
#

tahts not the same i sent or?

dull sequoia
#

that's called completing the square

#

it will turn out to be the same

white pebble
#

😔

dull sequoia
#

you can do that procedure to ax^2 + bx + c = 0

#

and then you will find that x = your formula

#

<@&268886789983436800>

white pebble
#

okay ill try

dull sequoia
#

if you get confused you can google this there are plenty of material online on this topic (completing the square)

white pebble
#

okay ill check

fathom jewel
#

Tim do you also need to study differentiation for the exam

white pebble
#

ableiten?

fathom jewel
#

yes

white pebble
#

ja klar

#

i mean with examen Abi gk

fathom jewel
#

Because you can also use this method to find the vertex (even though it is overkill)

white pebble
#

i always used the pq formula

dull sequoia
#

is that factorising?

white pebble
#

idk

fathom jewel
#

The pq formula is for the roots, but I guess you can also use the roots to deduce the vertex

dull sequoia
#

do you get something like a(x-b)(x-c)

white pebble
#

oh

#

wait no

#

vertex is extrema i got confused

dull sequoia
#

so to be honest there is another way

white pebble
#

for extrema i jsut do f'

dull sequoia
#

well that also works actually

#

i didn't know if you'd studied calculus yet because typically quadratics is taught long before calculus is introduced

#

there's also the method of using the axis of symmetry

white pebble
#

ye i maybe had it once but didnt needed it till yet

fathom jewel
#

This quadratic stuff is taught in middle school usually

dull sequoia
#

then you can plug in the point to know where the vertex is

#

yeah i learned about this in grade 8

white pebble
#

is this the vertex form of the example?

dull sequoia
#

<@&268886789983436800>

white pebble
#

<@&268886789983436800>

#

do u know why its only b/2 where i marked it?

#

shouldnt it be bx/2

dull sequoia
#

they've split it up

#

you see how in the left it's got a b * x rectangle

#

they cut that rectangle vertically into 2 pieces

#

1 of the halves got put horizontally under the square

white pebble
#

ye but why is it b/2 and not bx/2

#

that doesnt makes any sense

dull sequoia
#

The width is b/2

#

The area would be bx/2

white pebble
#

oh

#

im dumb

white pebble
#

how the hell did they simplified that

dull sequoia
#

Try expanding the bottom

white pebble
#

ye okay that makes sense but how did they do that

dull sequoia
#

They look at it and go oh I can factorise this

#

(Notice that they’ve constructed this part specifically so that they can factorise it)

white pebble
#

no

formal grail
formal grail
white pebble
#

wait i jsut realized

#

can i just cut the middle from x^2 + 2a + a^2 and take the x and a and square them?

#

does that makes sense?

#

ye i think i got it

#

but what do i do if i got functions like these

fathom jewel
#

3x+1 what is that graphically

white pebble
white pebble
fathom jewel
#

in the first one there is nothin so naturally?
-# also dont you recall x²?

fathom jewel
white pebble
#

the range of y is R

fathom jewel
#

yes

#

but the way you said "infinity" wont get you points

white pebble
#

okay i think im stupid

#

i thought to comlicated, if i try to imagine the functions in an coordiante system then this isnt hard

#

x^2 is the range of y, R > 0 ?

#

how do i say that

fathom jewel
#

positive y

#

but what about 0?

white pebble
#

wym

#

oh

#

its the >=

fathom jewel
#

can y=0 be attained

white pebble
#

whats attained

fathom jewel
#

angenommen werden

white pebble
#

fathom jewel
#

Do you know what range means in the first place for a function

white pebble
fathom jewel
#

yes

#

so my question is can y=0 be?

white pebble
#

yes

fathom jewel
#

for what value?

white pebble
#

x = 0

fathom jewel
#

yes

#

so you can state the range as [0,oo)

white pebble
#

how exactly would i write it as an answer

#

W = [0,oo)

#

?

fathom jewel
#

for example, if you denote W as Wertebereich

white pebble
#

yes

#

bruh okay thanks for the help

#

.close

safe radishBOT
#
Channel closed

Closed by @white pebble

Use .reopen if this was a mistake.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

rich echo
#

67

safe radishBOT
rich echo
#

.close

safe radishBOT
#
Channel closed

Closed by @rich echo

Use .reopen if this was a mistake.

median vigil
#

@rich echo Don't abuse the help channels.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

honest idol
#

yo this question i s regarding critical points on a 3D multi variable surface,

i need help understanding the intuition right when solving the system of equations, i just dont understand the correlation exactly here

honest idol
#

like when i took the partial derivatives, i got infinite tangent lines going in the x direction, and infinite tangent lines going in the y direction

#

but how does that exactly turn into two lines intersect where the intersection is their solution

#

(im assuming thats whats going on there)

#

also how do you tell if this a local minimum or maximum or an absolute minimum / maximum without graphing

quiet plume
quiet plume
honest idol
#

say you have an infinite differentiable 3D surface

#

and you take its partial derivative with respect to x

#

what this means is that for points in that space, y stays static and x changes

#

so for every point (x,y,g(x,y)), youre calculating the instantanious rate of change going from (x,y,g(x,y)) to (x+h, y, (fx+h, y))

#

ya know

#

so thats just gonna be a set of infinite parallel tangent lines pointing towards the x direction

#

and vise versa

quiet plume
#

At every point you get one line which is tangent to the surface with direction $\begin{bmatrix} 1 \ 0 \ f_x(x,y)\end{bmatrix}$ and one line with direction $\begin{bmatrix} 0\ 1 \ f_y(x,y)\end{bmatrix}$.

#

I wouldn't really think of them as infinitely many tangent lines in the x direction and infinitely many many tangent lines in the y direction though.

flat frigateBOT
#

Azyrashacorki

safe radishBOT
#

@honest idol Has your question been resolved?

quiet plume
#

The goal for critical points is that if you have an extremum somewhere at a point (x,y,f(x,y)), it ought to be the case that those two lines are just horizontal, i.e. they lie in some plane z=constant, i.e. the partials are both 0.

#

This amounts to solving the system of equations $$\begin{cases} f_x(x,y) = 0\ f_y(x,y) = 0\end{cases}$$.\

In this specific case you showed above, those equations are linear. Generally they may not be, you just need both partials to be 0 simultaneously at that point.

flat frigateBOT
#

Azyrashacorki

honest idol
quiet plume
honest idol
#

im tryna visualize it

quiet plume
#

There's lots of ways to interpret this.
It's the same as requiring that the tangent plane at that point be horizontal (like parallel to z=0).

honest idol
#

so that is at least 1 tangent line if a critical point exists

quiet plume
#

Both of the partials need to be 0 for the plane to be horizontal.

honest idol
#

i mean its just two orthogonal tangent lines

#

right

quiet plume
#

They're not necessarily orthogonal, but they will be linearly independent, which means they identify a plane, which is the tangent plane.

safe radishBOT
#
Channel closed

Closed due to timeout

Use .reopen if this was a mistake.

quiet plume
#

You could also interpret it without talking about tangent lines at all.
If f attains some extremum at a point, then it should be at a point where it doesn't change in neither the x or y direction (just like a 1-variable differentiable function has derivative 0 where it has a supremum)

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

twin prawn
#

Hello, dumb question, but what is the value of k here?

twin prawn
#

I'm asking because when I'm to solve, I might need to find the value of K

#

k

stoic torrent
#

Hello there

twin prawn
#

.close

safe radishBOT
#
Channel closed

Closed by @twin prawn

Use .reopen if this was a mistake.

twin prawn
#

OPS

#

.reopen

safe radishBOT
twin prawn
#

hello

stoic torrent
#

Right so for average rate of change,

#

You can simply apply change in R / change in T

twin prawn
#

nonono i get how toget the average rate of change and the inst

#

im asking for the value of k, cause the problem states that k is a constant

twin prawn
stoic torrent
#

you cant comment on value of k sadly

twin prawn
#

so just.. retain k as is

stoic torrent
#

Yeah

forest mountain
#

searching up the law gives k as a constant of 5.67*10^(-8)

stoic torrent
forest mountain
#

yeah

twin prawn
#

so what do i do? ill answer it with variable k? no need to sub k with the actual value?

stoic torrent
#

Unless the value of it has been mentioned to you

twin prawn
#

right

forest mountain
#

i would write the answer in terms of k if you don't know it like what yajant mentioned

#

just like answering in terms of pi or something

twin prawn
#

right

twin prawn
forest mountain
twin prawn
#

bet

#

thanks guys

#

.close

safe radishBOT
#
Channel closed

Closed by @twin prawn

Use .reopen if this was a mistake.

safe radishBOT
#
Available help channel!

Send your question here to claim the channel.

Remember:
Ask your math question in a clear, concise manner.
Show your work, and if possible, explain where you are stuck.
Do not immediately ping people or roles. After 15 minutes, feel free to ping <@&286206848099549185> once.
• Type the command .close to free the channel when you're done.
• Be polite and have a nice day!

Read #❓how-to-get-help for further information on how to ask a good question, and about conduct in the question channels.

upbeat swan
#

A two-compartment, closed container holds a mixture of 50% distilled water and 50% neutral vegetable oil. The mixture is left undisturbed in the laboratory for several days. During this time, the vegetable oil increasingly settles in the upper part of the container. This process occurs at a decreasing rate; that is, initially a large amount of oil settles in the upper part of the container per unit of time, but over time this process slows down. At the end of the observation period, all the oil has settled in the upper part of the container, and all the distilled water in the lower part. The following diagram represents the container, serves to facilitate understanding, and acts as a legend for the possible solutions.

nimble wyvern
#

!status

safe radishBOT
#
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
upbeat swan
#

What snapshots can be observed at the beginning of the period, at exactly

half the time, and at the end of the period?

#

I basically need to choose bwtween these options

#

The option that describes the liquids in the container

#

So im thinking

#

It has to be C or E

nimble wyvern
#

yes

upbeat swan
#

Becuase. B is in the wrong direction

#

A is linear

#

So its bad

#

And d is bad

#

And i was thibking

#

That

#

It should be E

#

Becuase

#

It says that the vegetable oil rises up

#

At first fast, then slower and slower

#

And C is basically the opposite because it rises faster and faster

#

This is my thought process

#

Am i wrong?

slate ingot
#

I feel like a mirror image of c would make the most sense

upbeat swan
#

Hm i dont follow

#

Becuase the curve of the upper half needs to increase

slate ingot
#

Thats why i said a mirror image

upbeat swan
#

Becuase more and more vegetable oil is at the top

slate ingot
#

Like, if you interchanged the position of the oil and water, then c would make sense

#

As it is, neither of the two make a lot of sense to me

upbeat swan
#

Yeah but the others are striaght up wrong

slate ingot
#

Id probably go with e, and then challenge this question afterwards

upbeat swan
#

So it has to be between C and E

slate ingot
upbeat swan
#

Ok so youre saying its E

#

Same as me

#

Now look at the solution

slate ingot
#

E is the most appropriate answer of the given options

upbeat swan
slate ingot
#

I believe the question is incorrect

upbeat swan
#

It makes no sense

slate ingot
upbeat swan
#

How is the process slowing down if the curve from C is increasing!

slate ingot
#

It makes sense if you take water on the right, and oil on the left

upbeat swan
#

Water is down and oil is up

slate ingot
#

Yes

upbeat swan
#

And im saying

#

If it says that the slope of the curve should be decreasing over time( cuz there is less and less oil going up over time)

#

Then how can it be C if the curve of C has a slope that is increading over time!

#

Increasing

slate ingot
#

Im saying that C is the correct option, but if and only if The water is on the right, and the oil is on the left, ie, a mirror image
The slope will then be decresing

As it is, neither of the 5 options are correct, unless the examiner decided to troll you and view the vessel from behind as opposed to the front

upbeat swan
#

I dont understand why you think its mirrored

#

The starting position is 50% 50%

#

Then

#

The curve that is above

#

In the upper half of the container

#

Goes towards 100% oil, so to the right

#

And the one in the bottom half goes towards 100% water , so to the left

upbeat swan
#

For the top half 100% is on the right side and for the bottom half the 100% is on the left side

#

So it's correct

#

The oil goes towards the right and the water towards the left

slate ingot
#

Well then, can you explain to me why there is more water in the upper portion in option E, when water is supposed to occupy the lower portion?

upbeat swan
#

Ugh this is frustrating

#

So my idea was that there are 2 graphs in here

#

Separated by the middle line

#

The curve in the upper half describes the percentage of oil in the upper half

#

And the curve in the lower half describes the percentage of water in the lower half

#

At first they are both at 50%

#

So a straight line through the middle

#

Then the curve describing the oil, so the curve in the upper half goes towards the right

#

And the one on the bottom goes towards the left

#

Becuase the oil and water reach 100% over time respectively

#

So this is exactly what we would have in E

upbeat swan
#

Only in the bottom half

#

So i guess we are viewing the problem in 2 fundamentally different ways

slate ingot
#

We are viewing a problem with no correct solutions imo

upbeat swan
#

Well usually these questions are solevd by eliminating the even worse options

#

Until the least worst remains

slate ingot
#

The curvature on E isnt correct
The curvature on C is correct, but they mirrored the graph

slate ingot
slate ingot
#

E is the most appropriate answer, but it isnt the correct answer

upbeat swan
#

Yet the book says its C

slate ingot
#

If this is something that showed up in once of your cram school/coachings tests, you can talk to your mentor about this question
Thats what we would do. And either the question would be cancelled, or it would be stated that they observed it from behind

slate ingot
#

Not all questions are correct yaknow

upbeat swan
#

Ok so im gonna assume that the answer is E

#

And that the model solution is wrong

slate ingot
#

Brother the question in itself is wrong

#

Unless its from a test or something, just strike it out

#

Because E will not get you any marks if this is a option present

upbeat swan
#

But this makes no sense

slate ingot
#

How so?

upbeat swan
#

At the end the oil has to be at 100%

slate ingot
#

This isnt the end my man

#

This is the middle part

upbeat swan
#

So how would your end look like

slate ingot
#

Precisely what you said

#

Oil is upwards, water is downwards

upbeat swan
#

So your end would look like the end from E?

#

Or like the end from B

slate ingot
#

E

upbeat swan
#

Hm so in the bottom half, your curve is heading towards the rightmost value

#

And you re saying that in the end, it will reach the leftmost value

#

?

slate ingot
#

What?

#

Im saying that oil will be up, and water will be down by the end

slate ingot
upbeat swan
#

Whats the x axis and the y axis

slate ingot
upbeat swan
#

Yeah but you gotta respect the x and y axis

#

They tell you that the x axis is the % of oil and of water

#

So you know that in the end you will get the end of E

slate ingot
#

I already told you, the book messed that up

upbeat swan
#

Nah

#

I explained

#

Why its correct

slate ingot
#

The curvature on E is incorrect

upbeat swan
#

Why

#

Do you understnad that there are 2 separate graphs?

#

Maybe it helps

#

If you cover the bottom part of the contained with your hand

#

So you just see the top half

#

Which represents

#

The oil

#

Which

slate ingot
#
  1. how is there more water above the x axis, and less water below the axis?
upbeat swan
#

Has to go towards 100%

upbeat swan
#

It starts with

#

50% water and 50% oil

slate ingot
#

Yes

upbeat swan
#

Now lets look at oil only

#

From the intitial 50%

#

In the top half of the container

#

It rises

#

Towards 100%

#

Towards the rightmost corner

slate ingot
#

Hang on a second

#

THATS WHAT THISE GRAPHS MEANT

#

I thought the Area was what we were looking at 😭

#

Thats totally on me

#

But then, why wont it be c?

upbeat swan
#

🤣🤣🤣🤣🤣🤣

upbeat swan
#

It says in the question

#

That

#

The oil is rising

#

But it rises slower and slower

#

So i was thinking

#

That this mens

#

Means

#

That the slope of the curve keeps decreasing

slate ingot
#

Yeah fair enough

upbeat swan
#

At first the slope is big then it slowly oges towards 0

#

So then i look at C

#

And I see that

#

The slope keeps increasing

slate ingot
#

I think i see the mistake

upbeat swan
#

It doesnt decrease

slate ingot
#

Look at the graph for the water portion, the slope is decreasing in c, and increasing in e

#

The slope for the graph of oil in c looks like its increasing, but its actually decreasing

#

The reference axis for the oil portion is the top right, not the bottom left

#

If you get what i mean

upbeat swan
#

Hm

#

So you re saying

#

That the slope of C is decreasing

slate ingot
#

Yeah

upbeat swan
#

How

slate ingot
#

Its concave downwards

upbeat swan
#

So we are only looking at the top part

#

Or?

slate ingot
#

The reference for the top part is top right

slate ingot
#

Ygwim

upbeat swan
slate ingot
#

Then youll need to take the top right as the origin

upbeat swan
#

The origin of what

#

Isnt the origin at 50%

#

In the middle

#

Thats the start

slate ingot
#

No

#

Not for determining the slope anyways

upbeat swan
#

🤮

#

I dislike this qurstion

slate ingot
#

🫂

upbeat swan
#

Ok

#

Lets just look at the top part

#

Just pretend that the bottom part doesnt exist

#

So the oil

slate ingot
#

Why

upbeat swan
#

We look at.

slate ingot
#

Why do you want yo make this harder for yourself

upbeat swan
#

Just like that

#

Nah just

#

Ignore the bottom

#

So

slate ingot
#

If youre going to look at the top part

upbeat swan
#

Oil goes from left to right, 0% to 100%

slate ingot
#

Then flip your phone around and look at thebottom part, thats whatll be more accurate

upbeat swan
#

We can take the line separating the compartments as the x axis

#

where x is the % of oil in the top part

slate ingot
#

Thats the fallacy

#

The midpoint is not the origin

#

This int a standard cartesian plane

winter whale
#

I like your name

upbeat swan
upbeat swan
#

Wait

#

No

#

Omg

#

🤮🤮🤮🤮🤮🤮🤮🤮🤮🤮

slate ingot
#

Real

upbeat swan
#

This is what i would do to that container

terse imp
#

heyyy

slate ingot
#

Sir this is #help

#

-# not that i have the right to say that

upbeat swan
upbeat swan
terse imp
#

How u guys doin

slate ingot
upbeat swan
terse imp
#

what are u guys discussing bout?

terse imp
upbeat swan
#

Its above

terse imp
#

ok lemme see

upbeat swan
#

Check the pinned message

slate ingot
upbeat swan
#

So anyways

#

How tf do we get a curve

#

If

upbeat swan
#

The middle photo

#

Is supposed to be

#

A single instant

#

From the midway of the process

slate ingot
upbeat swan
#

Its not a function

slate ingot
upbeat swan
#

Then wtf is it

upbeat swan
slate ingot
#

The vertical distance from the base is literally the point in the vessel

#

And the horizontal distance is like the mole fration curve in liquid solutions

#

The more you go to the left, the more water
The more you go to the right, the more oil

#

You get my point?

upbeat swan
#

Keep in mind that the end photo shows 2 lines

#

Separate

upbeat swan
#

And water in the bottom

#

I think

#

And look

#

If you look at the container from sideways

#

,rccw

flat frigateBOT
upbeat swan
#

You literally get

#

0-100

#

And 100-0

#

Idk

slate ingot
#

Nooo 😭
Initially its a homogenous emulsion of oil and water

#

Then it starts seperating out

upbeat swan
#

I think its like this