#precalculus

1 messages · Page 71 of 1

noble lava
#

So pretty difficult

hoary iris
#

I see

hoary iris
noble lava
#

I'd show you the solution except it would ruin the satisfaction of doing this yourself when you're done with limits and can execute things quickly

hoary iris
noble lava
#

Well you're just starting

hoary iris
noble lava
#

Also your question was 1^inf form and you said you learnt only 0/0

hoary iris
#

I have learnt that in my normal 11th

noble lava
#

Oh hsc?

hoary iris
noble lava
#

Same

#

My instructor was hella surprised when i started spitting lhospital to derive standard limits

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Bro was like stop, lhospitals is a weakness

noble lava
#

And until recently i didnt understand how true that was

hoary iris
noble lava
#

But now im stuck in my stubborn habits and i cant change how i do things

hoary iris
hoary iris
noble lava
noble lava
#

I just told you two opencry

hoary iris
noble lava
#

Ik theres some stuff like taylors as well but idk shit abt that

#

Will learn in college prolly

hoary iris
noble lava
#

Also keep in mind that series expansion is a very powerful weapon

#

Just learn it for sin cos and ln and you're set

hoary iris
noble lava
#

But now ik its easier and i do it occasionally

#

Not really been solving limits much tho recently, mostly indef integ

hoary iris
noble lava
#

The real question is why am i doing math daily in my vacation opencry

noble lava
#

Like ngl ive been in this server four days and

hoary iris
#

It may please minds of mathematicians lol

noble lava
#

Thats 500 messages per day

#

More math than i did in the week before mains opencry

hoary iris
willow bear
#

i have 768k messages and have been in this server for 8.5 years, calculate my rate of messages per day.

noble lava
#

Tho tbf most of it is easier since i usually only pick those i can answer acchese so i can help the asker

willow bear
#

if you need an exact start date: january 15, 2017

hoary iris
noble lava
#

,w 76810^3/(8.5360)

obsidian monolithBOT
noble lava
willow bear
#

please don't call me "brother" or any variation thereof.

noble lava
#

Im not calling you brother

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Its like

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"Bruh", the expression

willow bear
#

you called me "bruv" just now and i told you not to do that.

noble lava
#

Ok soz soz

noble lava
modest bolt
noble lava
modest bolt
#

monkey d luffy joined at that day

noble lava
#

O i didnt see what u replied to lol

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,w 4404/446

obsidian monolithBOT
noble lava
#

,w 2202/23 in decimals

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Ooh

obsidian monolithBOT
noble lava
#

Lmao period 22

#

That's a hell of a thing to do by hand opencry

noble lava
hoary iris
#

in this server

noble lava
#

What why did he say 2024 then lol

hoary iris
#

about 3 years

#

idk

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lol

hoary iris
#

eventhough only 4000 msgs lol

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but you lol executor

noble lava
#

Fr

hoary iris
#

I will come sometimes to help

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sometimes to get help

noble lava
#

Well i have nothing to do rn except do coding math and games

hoary iris
#

sometime to chill

noble lava
#

Vacations are pog

hoary iris
noble lava
#

In a month

#

College begins

hoary iris
#

anyways enjoy your vacation prolly

noble lava
#

But its fine ive been on holiday for 20 days already

noble lava
hoary iris
#

lol

noble lava
#

Why does everybody tell me to watch one piece its a thousand episodes catsob

#

The longest anime ive watched is naruto

hoary iris
#

You won't regret watching it

noble lava
#

Ive watched like 50+ anime till now nothing is close to 1000 episodes

noble lava
#

Rn I'm watching peaky blinders tho

hoary iris
noble lava
#

Thomas shelby catking

noble lava
hoary iris
#

not only that though

noble lava
#

What's the next longest

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After op

hoary iris
#

aot?

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or ds

noble lava
#

You've watched?

hoary iris
noble lava
#

O

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One anime i hate is mha

noble lava
hoary iris
hoary iris
hoary iris
noble lava
#

Disappointment in 2 episodes

hoary iris
noble lava
#

Just what is that shit

noble lava
hoary iris
#

you will die in oda's foreshadowing lol

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lol

noble lava
noble lava
hoary iris
noble lava
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Me allen too lol

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This wasnt so developed in my education period tho we just did things on whatsapp and offline

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Good to know theyve integrated some stuff

hoary iris
#

I am allen online

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btw

noble lava
#

O makes sense

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How is online?

hoary iris
#

good for my tight schedule of school

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but too hard

noble lava
#

Oh you go to a real school?

hoary iris
#

to keep up

hoary iris
noble lava
noble lava
hoary iris
#

but I am in a real problem

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lol

noble lava
#

Hard to do real school exam though

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But i concentrated so it was easy

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Got 197/200 in cs so that just clutched big time

hoary iris
noble lava
hoary iris
noble lava
#

Oh long time

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Allen lectures when

hoary iris
hoary iris
noble lava
#

O so school close to home

noble lava
#

Bifocal cs

noble lava
#

Never sacrifice sleep tho btw

hoary iris
noble lava
hoary iris
#

sleeping at 12

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normally

noble lava
#

Nice

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Ive seen lot of jee ppl do it

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Long term mein pachtayenge

hoary iris
noble lava
#

I tried for 2 weeks during jee

noble lava
#

Pachtayenge= will regret

hoary iris
noble lava
#

You're nri?

hoary iris
noble lava
hoary iris
noble lava
hoary iris
#

south lol

noble lava
#

Yeah

hoary iris
noble lava
#

I speak kannada

hoary iris
noble lava
#

Still thinking tho not decided

hoary iris
noble lava
#

Also were talking in precalc

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Lets go disc 2

hoary iris
#

yeah we may die here

noble lava
hoary iris
#

ping me

modest bolt
#

and i will awooDEMON you if you talk here now, if you wanna say something to me, ping me in #chill

burnt cape
#

Hey @wraith escarp sorry to bother you, but is this a corner?

wraith escarp
#

there are two different slopes at that point, aka the derivative is discontinuous

burnt cape
wraith escarp
#

itll be f'(x) = 0 until -1, then start being f(-x) = -1 after that

burnt cape
#

im confused on how to graph that on f'

wraith escarp
burnt cape
#

Like this?

wraith escarp
# burnt cape Like this?

a) the slope isnt -2 for the downward part of the graph
b) there should be another jump at x = 3 since f(x) starts going up

wraith escarp
#

not correct past x = 3

burnt cape
#

so at 4?

wraith escarp
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whats the slope at x = 4 and whats it at x = 5?

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does it change?

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if not, why does your f'(x) change

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also, speaking of which, what is the slope of f(x) at x = 4?

burnt cape
#

i doesnt change and the slope at x= 4 is 1

wraith escarp
burnt cape
wraith escarp
#

you are making random lines

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the slope at x=4 is 1 as you mentioned

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therefore f'(4) should be 1

burnt cape
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is it not 1 though since it passes through (4,4)

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which slope is 1

wraith escarp
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you arent trying to make the slope of f'(x) match the slope of f(x)

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the actual y value of f'(x) is the slope

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f'(x) should contain (4, 1) because the slope of f(4) is 1

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it should also contain (5, 1) for the same reasons

burnt cape
wraith escarp
#

whats the slope at x = 3.5

burnt cape
#

nothing so i have to make it go to the 3

wraith escarp
#

what do you mean nothing?

burnt cape
#

well theres no line there i jumps from 3 to 4 so shouldnt it be

wraith escarp
wraith escarp
#

the slope at x = 3.5 is also 1

#

and your new correct answer does in fact have (3.5, 1) so its looking good

burnt cape
#

so can you walk me through the steps again

wraith escarp
#

i mean your answer is right, do you have questions about specific parts of it?

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ie why some things are how they are or how we got something specific?

burnt cape
#

im just confused why we used straight lines for everything even though after the dashes it goes up

wraith escarp
#

well

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"it goes up" is the misunderstanding

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the function does go up, but the slope doesn't

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x = 0, 1, 2 all have the same slope

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it doesnt "go down"

high steeple
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any tips on memorizing very long formulas for someone with weak memory? 🥀

river drift
#

you shouldn't be in a situation where you need to memorize very long formulas

high steeple
#

what about college entrance exams

willow bear
#

yeah can you show the long formulas you're finding yourself having to memorize

high steeple
#

ive never taken an entrance exam so idk what to expect

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example here

high steeple
willow bear
#

well, this formula's written in a rather unwieldy way, but if you aren't familiar with sigma-notation it might be a bit unavoidable.

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though again i would advise AGAINST memorizing it into a thousand fragile pieces

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and instead learning about binomial expansions in depth

opal sable
arctic dagger
#

it's also not very hard to memorize

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like you should see the pattern in binomial expansion formula

opal sable
#

yeah.

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but what about other formulas

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but anyways, how its derived is the main part

willow bear
#

i think that the longest formula worth "memorizing" is the law of cosines

arctic dagger
#

true

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for me personally it's worth deriving

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I'm still on my quest to get used to it by deriving

willow bear
#

its derivation is pretty important to know

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but at the same time, when you're practicing with it, thinking about the derivation every single time gets taxing

hushed sphinx
willow bear
#

about the same length innit

#

$c^2 = a^2 + b^2 - 2ab \cos(C)$

or maybe

$\cos(C) = \frac{a^2+b^2-c^2}{2ab}$

vs.

$x = \frac{-b\pm\sqrt{b^2-4ac}}{2a}$

obsidian monolithBOT
hushed sphinx
#

Hmmm, the quadratic formula feels more involved to me ... but I acknowledge that is not an exact science.

#

(Ironically, I can remember the quadratic formula, but I need to look up the law of cosines).

ionic ether
willow bear
#

yeah i was just giving both forms to make a comparison on complexity/perceived "length"

willow bear
#

oh yeah hm

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that's longer innit

hushed sphinx
#

Is that worth memorizing, though?

willow bear
#

yes imo it is

hidden sun
#

Every formula is worth memorizing if it saves your time

hushed sphinx
#

Hmm, at least I've never bothered. If I need it, I'll either look it up, or derive it from e^it.

hidden sun
#

Only do it if you know how to get them at any moment

willow bear
hidden sun
willow skiff
#

<@&268886789983436800> spa

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spam

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Moderators Need A Spa Day

hushed sphinx
willow skiff
#

here ya go

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ya filthy American

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if you have x^2 + px + q, so you just need to divide b and c by a

hushed sphinx
#

I'm not American either.

willow skiff
#

ah

hoary iris
#

lol

vagrant nymph
#

Is my solution correct?

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It feels wrong

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But the ans is correct

void charm
#

behold the final boss of basic geometry, superior Menelaus's formula

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I mean basically this is harder to memorise than any formula

modest bolt
#

BP × AM/MB = AN/NC × PC
idk why I feel this is easier to remember

willow skiff
#

triangles APN and NPC are related by scaling

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and so are triangles AMP and BMP

modest bolt
#

ngl Idk how does that reveal any proof but I really meant I only feel like writing the same equation like that is easier to memorize, not like I know how to prove the equation flonshed sad

storm lodge
#

its quite easy to memorize if you solve problems with it

sly cipher
willow skiff
modest bolt
willow skiff
#

oop- ah

#

the name is so shit, cause it could also refer to right angle inside a circle

vagrant nymph
hollow fractal
# vagrant nymph Is my solution correct?

I would love to help but i can't read english handwritings.
From what i can read you calculated: (1+m/8x)^(1/3) = (1+m/24) ?
Correct me if i'm wrong or they're symbols i don't know about

hoary iris
#

,, \sum(ab)=\sum(a)\sum(b)?

obsidian monolithBOT
#

Monkey•D•Luffy

willow bear
#

does not even work for sums 2 terms long 💀

drifting oyster
#

Trust me bro

obsidian monolithBOT
#

Enterlessguy

hoary iris
hoary iris
#

convert a and b into x?

drifting oyster
#

well I was assuming you were using sequences for a and b

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So just let the sequences be defined for R instead of N

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Trust trust

willow bear
#

for the record, i will be a killjoy on purpose and say that @drifting oyster's thing is completely false and also nonsensical.

hoary iris
willow bear
#

ok yeah this sort of naïveté is exactly why a space like this needs to be free of falsehoods stated so brazenly as @drifting oyster did

hoary iris
#

I thought it is true since sum and integral has some relations to each other

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I thought It is super helpful

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but so sadly it is not true

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for my unfortune

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lmao

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Also @modest bolt Do you know the relation b\w sum and int?

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Are you writing the relation????

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If yes, nvm me lmao

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Hell you really did write the relation

modest bolt
#

int is just infinite summation of smaall x but you can know better by google

noble lava
#

You should understand reln betn integral and sum by looking at the example of an area under the curve problem

modest bolt
noble lava
modest bolt
#

there are good animation vedios to explain that, you can watch if you want

noble lava
#

Yeah

gray magnet
#

i know there is a formula for this

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why does this not work

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it works for one but there is another

raw hill
gray magnet
raw hill
gray magnet
raw hill
#

What

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That tells you if this angle is 5pi/12 (absolute difference between the two angles with the x axis is the indicated angle by exterior angle theorem)

#

But my point is that this angle could also be 7pi/12

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Because then the acute angle would be pi-7pi/12=5pi/12

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@gray magnet Hello?

gray magnet
#

i forgot that arctan only gooes anticlockwise

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i though it would account for this

final ore
#

i know its not in english

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but why is that the k is going to n-1?

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shouldn't it be both k=0 to n?

abstract musk
#

can someone please explain why the null set is a subset of all the other non-empty sets...I mean the null set doesn't contain any element of another Set.

distant ivy
final ore
#

ahhh

cinder wyvern
#

hey

#

im learing deriviatives rn

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i like calculus its very fun

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what can i expetc next

silent vine
cinder wyvern
#

nice!

rough arrow
#

tfw you realize 1/x looks the exact same as 1/y

rough arrow
# cinder wyvern what can i expetc next

more derivatives, and antiderivatives, and going back to limits again, and then back to derivatives, oh and you remember that math trick you forgot from middle school? yeah you're gonna use that again, but only for a week.

m. a. t. h.

solar dagger
#

can anyone tell me the definitions of tangent lines, cause it seems like its really useless and rendundant to me

#

from what i know Tangent line is a point in a curve that sort of like kisses the point that from the lines itself it goes forever, but then Why do we need all of this fancy Formula and others just to decide that one point

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and what is actually the use case of this tangent line?

soft plover
#

it is used to calculate the slope of a curve at a certain point

solar dagger
#

isnt tangent line return a line equations

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rather then a slope

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cuz if u want a slope u can just use the point slope formula for it

whole void
whole void
#

I think there are subtle differences with this and the calculus definition I believe

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what do u think? @solar dagger

solar dagger
#

but while solving the tangent line problem itself we can know the Slope of it as we most of the time

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will need to find the slope first

solar dagger
whole void
solar dagger
#

then wdym?

whole void
#

No I don’t know what u mean

soft plover
solar dagger
#

if im wrong and u dont know what i mean then i dont know what that mean either.

whole void
whole void
whole void
solar dagger
#

but i think i already got the definitions of tangent line it self, just finished doing some research

solar dagger
#

its basically a Direction from point a to be point b

willow skiff
willow skiff
whole void
willow skiff
solar dagger
willow skiff
#

when you start using open intervals you'll have lost them already

solar dagger
willow skiff
#

x-coordinate = a
y-coordinate = f(a)

solar dagger
#

but why u use function?

#

is there any special reason on that?

willow skiff
solar dagger
#

also tangent line always return a line equations right not a slope? correct me if im wrong.

willow skiff
#

it's just not phrased in the language of calculus

#

that's moreso a geometry definition

whole void
solar dagger
willow skiff
willow skiff
solar dagger
solar dagger
willow skiff
#

a lot of functions like sine and cosine, or e^x aren't polynomials

solar dagger
#

what is that?

willow skiff
solar dagger
#

also if u dont mind can u tell me the basic about taylor series, i heard it was very beautiful and fun

willow skiff
#

as you move away, to the left and to the right, the approximation gets less accurate

solar dagger
#

havent learn about it at all though

solar dagger
willow skiff
willow skiff
#

we approximate the function at x = 0

solar dagger
willow skiff
#

we don't necessarily have y = 0

#

y-coord could be anything

solar dagger
#

alright alright lets talk about the taylor later

solar dagger
#

also back to the Tangent line

willow skiff
#

ok

solar dagger
#

usually the formula for tangent line is what? i asked ai and it says it was the point slope formula

#

im not sure if that is right though

#

lets say a circle

solar dagger
#

i want to find a tangent line of a circle, did the formula will be different for like a Box/triangle.

solar dagger
whole void
#

I know what’s it’s trying to say, but the locally part makes it weird. Like how are these two different

solar dagger
willow skiff
solar dagger
#

i thought its only touch

willow skiff
#

it is a tangent line where it says 'touches here'

willow skiff
whole void
#

south what’s that pfp btw

solar dagger
# willow skiff what do you want to know

woah oke uhm this going to be pretty long conversation, cuz i always ask things too much most of the time.

soo like lets say i want to find a Circle tangent line, how can i do that?

willow skiff
#

watch this it'll teach you how

whole void
#

if u remember geometry

willow skiff
#

yeah that's another approach, by similar triangles

solar dagger
solar dagger
#

rn

solar dagger
whole void
whole void
solar dagger
#

u referring to the standard form or general?

#

like the

whole void
solar dagger
#

(x + h)^2 + (y + k)^2 = r^2

if im not wrong

#

u talking about this?

willow skiff
willow skiff
solar dagger
#

gtg now, need to wathc the video rq

#

then ill get back to here

willow skiff
#

you don't need any equations to realise that

willow skiff
#

but then that's a bit overkill if you only want to know for circles

whole void
willow skiff
whole void
#

eg the slope of the radius is 5/3 so the slope of the tangent line is -3/5

whole void
solar dagger
#

@willow skiff

#

just finished watched it, btw what is the different between Calculus method and geometric method on finding the tangent lines of a circle?

#

did calculus more accurate or what is the different?

willow skiff
solar dagger
#

but the result will stays the same?

willow skiff
#

once you find f'(a) you can just sub into $y - f(a) = f'(a) (x - a)$

obsidian monolithBOT
willow skiff
solar dagger
#

i see yeah i think ill stick with geometric for now, until i understand calculus more

#

also what about if like a Box?

willow skiff
#

yeah i didn't realise you just wanted the circle

solar dagger
#

no no i mean

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a curve

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how can i find the tangent line for a curve?

willow skiff
solar dagger
#

up and down

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or quadratic curve

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or cubic curve

willow skiff
willow skiff
solar dagger
willow skiff
rough arrow
willow skiff
#

it's based on finding the slope of the line as you bring two points closer and closer together

#

when those two points are the exact same, that limiting slope gives you the slope of any curve

rough arrow
solar dagger
rough arrow
#

and it'll be easier each time

solar dagger
#

yeah sure ill learn it

willow skiff
#

for circles we use the fact that the tangent and radius angle is 90 degrees

#

that's only for circles

solar dagger
willow skiff
#

there's a few other classes of functions where you don't need calculus, excluding lines

solar dagger
#

or wrong

willow skiff
#

but then you'd have to be smart to think of how you could do it without calculus

willow skiff
solar dagger
#

Oh oke wait wait

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let me think rq lol

rough arrow
willow skiff
#

yeah it's a natural extension of point slope form

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you literally replace m with the derivative at x = a

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that's it

rough arrow
#

oh lol i'm hella behind

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on the chat

solar dagger
solar dagger
#

ohhh

willow skiff
#

only true for a circle

solar dagger
#

so its perpendicular

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woooooooahhh but i still got question about circle since u talking about circle

rough arrow
#

circles are triangles and triangles are harmonic swings and harmonic swings are vibrations and everything is everything

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QED ⬛

solar dagger
#

in circle geometric formula there is an extra (x - h) and (y-k)

and why is that? i mean the rest its similar to the standard form of Circle just with extra (x - h) and (y - k) also when i calc it, it seems like used for multiplication kind of thing but i believe there is a deeper Meaning in it.

solar dagger
rough arrow
#

hehehehehehehehehe

solar dagger
#

like the unit circle uses triangles for the circle

rough arrow
solar dagger
solar dagger
#

maths guy always ask for a reason and prove.

rough arrow
#

Are you talking about the -h and the -k?

solar dagger
#

(x - h)² + (y - k)² = r²

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and this is for the circle standard form itself

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it looks pretty similar except for the

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extra (x-h) and (y-k)

rough arrow
#

they're the same, though.

#

no, they're the same. 🙂 look closer.

solar dagger
#

yeah but they produce a different

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equations

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and result

rough arrow
#

the difference is....
one has an x and an x_1 <--- one is symbolic, one is defined
the other has two x <--- both are symbolic

solar dagger
#

yes i know that but

rough arrow
#

it's the same formula, but you're picking points for the tangent line, so you take up two of the coordinates

solar dagger
#

they two is different

#

try to plug some random coordinate of a circle

rough arrow
#

lol, I should be more careful with my words.

willow skiff
solar dagger
#

i think this is right

willow skiff
#

$x \mapsto x - h$ moves the function $h$ units to the right

rough arrow
#

They're the same, as in, the tangent line equation is derived from the original equation

obsidian monolithBOT
solar dagger
#

dont use that kind of explanation i beg u

#

i wouldnt understand it at all lol.

willow skiff
rough arrow
#

It's not "extra"... (x-h)(x-h) = (x-h)^2

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but in one, we "define" the x

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and the y

solar dagger
willow skiff
#

here I'll link a vido

solar dagger
solar dagger
#

let me think rq

willow skiff
# solar dagger havent learn that at all ngl.

Now that we know the basics regarding graphing algebraic functions, it's time to learn some tricks that will come in handy as we graph different kinds of functions. Specifically, there are terms inside functions that do very predictable things to graphs, and if we learn what these are, we can look at certain functions and quickly graph them with...

▶ Play video
solar dagger
#

ohh that is right @rough arrow

rough arrow
#

such as, if a known point on the circle is (5,2) then x1=5 and y1=2
so
(5-h)(x-h)+(2-k)(y-k)=r^2

willow skiff
#

you can't start calculus without having a deep understanding of functions

solar dagger
#

the x_1 and y_1 is uses for the tangent coordinate

solar dagger
willow skiff
#

here's another example of what I mean

willow skiff
rough arrow
#

yep yep yep!

another fun one to realize... point-slope form? y-y1=m(x-x1)... that's 100% equivalent to y=mx+b, just written out so we can recognize exact points in the formula, which is therefore easier to create tangent lines

solar dagger
rough arrow
#

Check out something like OpenStax for a free textbook!

#

My school uses this book for our course 🙂 and it has practice software in it, too!

solar dagger
willow skiff
#

James Stewart's Precalculus for example

rough arrow
#

Desmos has free(?) lessons and calculator toys too

willow skiff
#

yeah even if you follow Khan Academy you won't be that far off

#

at least it's organised and there's quizzes on every subtopic

rough arrow
#

and you get energy and plants and superpowers and stuff, lol

willow skiff
#

YouTube is good but it's not a replacement for an actual curriculum

solar dagger
rough arrow
#

I love Khan but I don't use it consistently enough hahaha

willow skiff
#

I do think you shouldn't stress about if you're "ahead" or "behind" or not

solar dagger
#

i often jump from another to another and yet i still understand it. but at a different concept like this im loss

willow skiff
solar dagger
#

it might sounds abit funny that i know trig but not function transformation fully

#

so yeah i guess ill try

willow skiff
solar dagger
solar dagger
willow skiff
#

you know what the a, b, c, d do?

solar dagger
#

the inside bracket shift or make it strecht

#

and the outside is

willow skiff
solar dagger
#

for vertical shift

willow skiff
#

see how you go

willow skiff
willow skiff
#

but you haven't realised that it's the same for all functions

willow skiff
solar dagger
solar dagger
willow skiff
#

most importantly practice the exercises

#

answers are online somewhere

solar dagger
#

wow the website is actually full of e-book about math thanks @rough arrow

solar dagger
#

or something else?

rough arrow
# solar dagger yeah so now i just need to know the reason behind it, by learning function trans...

the reason is because of math, lol. i apologize if my descriptions are hella basic right now... i'm super tired, but here's why:
if we know a number is, say, 5, but we want to find a spot where it equals 3... we do math.

  • 5-3=2, hey dope, we found a 3 in there!
    but what if we're dealing with x & y at the same time?
    well, same thing applies. use point-slope form. (I can't think of a good example right now... too sleepy, but I hope this shows how it's more simple than it seems)
#

lol i keep falling behind in the convo lollllllllllllllll

willow skiff
#

you can browse multiple books to see which one explains the best as well

#

main thing is just read and practice

#

if anything is unclear watch YT

#

but try to follow the book if you can

rough arrow
#

I'll add that I'm taking Calc 2 this summer, and the nice thing about Algebra, Pre-Calc/Trig, Calc 1, 2, 3... they all just build off each other.

solar dagger
# rough arrow the reason is because of math, lol. i apologize if my descriptions are hella bas...

yeah math is got alot alot of abstraction someetimes its just like really intresting and annoying to find the reason on why this happend or this happend because usually at school we only teached to remember something and the teacher doesnt even tell us the reason behind it, also you are right in every math formula there is alot lot lot of possiblity going on like a number 5 and 3 can become a coordinate or it can become this and bla bla bla.

rough arrow
#

sometimes linearly... one chapter builds to the next chapter

willow skiff
#

yeah literally don't look at anything before precalc

solar dagger
#

thanks man!

willow skiff
#

there's a lot of repetition

#

you don't need to look at alg 1 or alg 2 if you learn precalc properly

solar dagger
willow skiff
rough arrow
#

other times in spirals... you'll learn a trick, put it on your reference card, then not use it for a while until you remember it exists when you're stumped 3 chapters from now

solar dagger
rough arrow
#

hence my joke earlier about "remember that math trick you learned in middle school?"

#

because really, math curriculum really just goes in spirals, endlessly 😆

willow skiff
#

if you're self-studying you don't follow what your school or your teacher is doing, by definition

#

you can go at your own pace

#

also a lot of schools have mandatory hours for learning mathematics and teachers need to find a way to fill up the time somehow

rough arrow
#

"hey, i know you're in the middle of some complex integration, but did you forget how fractions work?" <-- happens more often than you'd think, hahahahaha

willow skiff
#

about the spiral anology, which is very very useful and it's true

solar dagger
#

alright i gtg now guys, really glad that i meet you two, i learned alot today about how to learn and this tangent line.

#

thank you : )

willow skiff
#

after you learn precalc then you'll find that calculus uses precalc a lot, obviously

#

so you can revise precalc and learn calc at the same time

#

main thing is try to learn it well right now

#

90% of all calculus mistakes are caused by not understanding precalc

rough arrow
#

some of the precalc lessons are secretly teaching you calc... then you get to calc and learn it for real and go "hey waitaminute, this looks familiar!!!"

steady peak
#

Yello have a quick question, hopefully not interrupting anything
If I took precal dual this year, could I js take the precal AP test next year w/o taking the class

#

I feel like the class would lwk be the same, I only would have to study the frqs?

rough arrow
#

oh lol yeah, that's how AP stuff works.

steady peak
#

How do you even do math frqs tho

rough arrow
#

when you take the test, don't be me and forget to write down the time

steady peak
#

I'm also take AP calc ab this coming school year

willow skiff
rough arrow
#

lol, i showed up to math period and was like "where is everyone?"... teacher said "lol, the test was like 5 hours ago man, you missed it"

willow skiff
#

I will say practice with the formula booklet and underline the key bits of the question

hoary iris
#

Why $\sum_{k=1}^{\infty}\frac{1}{k^2}$ converges to 2 while $\sum_{k=1}^{\infty}\frac 1k$ diverges?

obsidian monolithBOT
#

Monkey•D•Luffy

uncut mulch
#

to 2? do you mean pi^2/6?

#

series for 1/k can be shown to diverge from integral test

hoary iris
#

I thought it is 2

#

,, \sum_{k=1}^{\infty}\left(\frac{1}{2^k}\right)

obsidian monolithBOT
#

Monkey•D•Luffy

hoary iris
uncut mulch
#

that will be 2, yes

hoary iris
uncut mulch
#

basic integral approach allows you to show that the sum is less than 2

#

getting the value of pi^2/6 is more complex,
(Basel problem)

hoary iris
#

also this is more interesting that $\lim_{n \to \infty}\sum_{k=1}^{\infty}\frac{1}{k^n}=1$

obsidian monolithBOT
#

Monkey•D•Luffy

hoary iris
#

or me?

willow skiff
hoary iris
#

raijin? lol

whole void
willow skiff
#

it happens

#

that's why these hidden assumptions (incl continuity) are super important

whole void
river drift
#

another problem is that you can have a function which is differentiable but crosses its tangent line infinitely many times in any open neighborhood of the point of tangency, e.g. x^2 sin(1/x)

willow skiff
#

ah I forgot about that

noble lava
whole void
river drift
#

but i think that the definitions are at least equivalent for twice-differentiable functions whose second derivative has constant sign in some open interval of the point of tangency

whole void
river drift
#

i had the idea of allowing it to be above on one side and below on the other, but upon closer thought that would clearly allow lines which just cross without tangency, so i'm not really sure

whole void
#

It does feel kinda odd like geometrically for sin(x) to have a tangent line at x = 0. I don’t think there’s a way to fix it then

#

like if u r using the “touch but doesn’t cross locally” definition

river drift
#

yeah. i think that the "touch but don't cross" notion seems to be a way of trying to enforce "pointing in the same direction" without explicitly invoking that notion, but the more we dig into it the less those seem to line up

whole void
river drift
#

as in, touch but don't cross and the ordinary derivative definition (which attempts to directly formalize "pointing in the same direction") seem to match less under scrutiny

whole void
#

I think both are formalized. I think they have different ideas of course

hoary iris
#

Is $\frac{\sin x}{x}=\prod_{k=1}^{\infty}\left(1- \frac{x^2}{(k\pi)^2}\right)$?

obsidian monolithBOT
#

Monkey•D•Luffy

willow bear
#

yes

hoary iris
#

Is $\prod(ab)=\prod(a)\prod(b)$? @willow bear

obsidian monolithBOT
#

Monkey•D•Luffy

hoary iris
#

I think this works for the case of prod

#

right?

willow bear
#

well this is kind of horribly written but like

#

yes i guess

hoary iris
#

how to perfectly write it

willow bear
#

i mean $\prod (a)$ is... vague

obsidian monolithBOT
willow bear
#

i would have rather seen you write something like

#

$\prod_{k=1}^n (a_kb_k) = \prod_{k=1}^n a_k \cdot \prod_{k=1}^n b_k$

obsidian monolithBOT
willow bear
#

something like this

#

also infinite products are quite finicky

hoary iris
#

,w finicky

willow bear
#

look up unknown words there

whole void
hoary iris
#

Do we should take extra care to infinite products? @willow bear

willow bear
#

you should exercise extra care when dealing with infinite anything

#

not just products

hoary iris
#

may it be trickier than normal

hoary iris
whole void
#

is there anything trickier about infinite products rather than sums?

hoary iris
#

@whole void Which grade are you?

hoary iris
#

,, \prod_{k=1}^{\infty}{\frac{(k+2)(k-1)}{k(k+1)}}=\frac{\prod_{k=1}^{\infty}(k+2)\prod_{k=1}^{\infty}(k-1)}{\prod_{k=1}^{\infty}k\prod_{k=1}^{\infty}(k+1)}

obsidian monolithBOT
#

Monkey•D•Luffy

hoary iris
#

Can this be true? @willow bear

willow bear
#

no, $\frac{\infty}{\infty}$ is a bad idea

obsidian monolithBOT
hoary iris
#

,, \prod_{k=1}^{\infty}{\frac{(k+2)(k-1)}{k(k+1)}}=\frac{\prod_{k=1}^{\infty}(k+2)\prod_{k=1}^{\infty}(k-1)}{\prod_{k=1}^{\infty}k\prod_{k=1}^{\infty}(k+1)}=\frac{k-1}{k+1}?

obsidian monolithBOT
#

Monkey•D•Luffy

willow bear
#

ok no that's just very wrong

hoary iris
willow bear
#

what, to calculate this infinite product?

hoary iris
#

yep!

willow bear
#

hm

#

there probably is but you won't like it

hoary iris
#

Just the approach is enough

hoary iris
willow bear
#

but i would look at the n'th partial product of that thing (ie instead of taking all the terms to infinity, look at the product of just the first n terms) and then cook up some magic with stirling's approximation formula

#

or whatever else is appropriate

#

maybe you won't even need stirling

#

maybe it can be done with just careful factorial bashing

raw hill
#

It telescopes tbf (assuming you meant to start from 2 instead of 1)

willow bear
#

that it might

hoary iris
#

,, \prod_{k=1}^{\infty}{\frac{(k+2)(k-1)}{k(k+1)}}=\lim_{n \to \infty}\prod_{k=1}^{n}(1-\frac{1}{^{k+1}C_{2}})?

obsidian monolithBOT
#

Monkey•D•Luffy

willow bear
#

may be correct but i don't think it's helpful

raw hill
#

Did you mean to start from k=1 b/c the term for k=1 is equal to zero

hoary iris
#

lmao

hoary iris
#

sorry for the mistake

raw hill
hoary iris
#

I got this prod from that comb lmao

#

Idk how to telescope it @raw hill

#

it is confusing

modest bolt
#

idk if its correct or not kekw but looks correct

raw hill
#

Starting at k=2, it’s (n+2)/(3n)

modest bolt
#

oh

raw hill
obsidian monolithBOT
#

Civil Service Pigeon

raw hill
#

What id do here is notice that (k+2) and (k+1) differ by 1

#

As do (k-1) and k

#

So that’s where we’ll get the most “immediate” cancellation

#

You may not see what I mean rn, but it’ll make sense later

#

Because of this, I’d split the product up as follows: $$\prod^{n}{k=2} \frac{k+2}{k+1} \cdot \prod^{n}{k=2} \frac{k-1}{k}$$

obsidian monolithBOT
#

Civil Service Pigeon

raw hill
#

Now, try writing out the first few terms of each of these products

#

And see what you notice

#

@hoary iris

hoary iris
#

but can't for division

raw hill
#

$\prod a_k b_k=(\prod a_k)(\prod b_k)$ as long as everything is well defined

obsidian monolithBOT
#

Civil Service Pigeon

raw hill
#

Which should be easy to see

hoary iris
#

@raw hill

raw hill
hoary iris
#

I see

raw hill
#

Ex. This infinite product is 1/3 (which I’ll let you work out later)

#

But $\prod^{\infty}_{k=2} \frac{k+1}{k^2}$ is zero

obsidian monolithBOT
#

Civil Service Pigeon

raw hill
#

But by splitting the infinite product as you did, they’re indistinguishable

raw hill
#

Then take the limit

#

This way you don’t run into issues with orders of infinity in the middle of your process

hoary iris
#

What is partial products/sums?

raw hill
#

Find the general formula of the product up to the nth term

willow bear
#

oh wait finite ones

#

mb

#

was about to say shit diverges

hoary iris
raw hill
#

k

hoary iris
#

one min or two min

modest bolt
#

what are you trying to do here? @hoary iris

raw hill
#

Find the partial product by telescoping and then take the limit

hoary iris
modest bolt
#

why making it hard, you can simply expand and see all terms cancel out and you left with 1/3

hoary iris
#

,, \frac{n+2}{3n}

hoary iris
#

@raw hill

#

I think I am done

#

@modest bolt Tell your idea btw

raw hill
#

Also I was breaking it down because

#

Yk they’re new to this

raw hill
hoary iris
raw hill
#

I don’t know what that’s supposed to show

hoary iris
#

from n=2

#

yes sorry

#

it is n+2

#

I mislatexed it

obsidian monolithBOT
#

Monkey•D•Luffy

raw hill
#

And now to find the infinite product, we can take the limit of this as n goes to infinity

#

@hoary iris

#

What is that limit

raw hill
hoary iris
#

,, \prod_{k=2}^{\infty}{\frac{(k+2)(k-1)}{k(k+1)}}=\frac{\prod_{k=2}^{\infty}(k+2)\prod_{k=2}^{\infty}(k-1)}{\prod_{k=2}^{\infty}k\prod_{k=2}^{\infty}(k+1)}=\frac{2-1}{2+1}

#

It does work

#

right?

raw hill
#

For the reasons I said earlier, this is very abusive

#

But if you want to write this as informal scratch work that isn’t meant to be read

#

Go ahead

hoary iris
#

It is very hard to read but applicable

obsidian monolithBOT
#

Monkey•D•Luffy

hoary iris
#

which is 1/3

#

pigeoooooooooooon

#

@raw hill sorry for pinging you repeatedly

#

@modest bolt What are you typing so hard and didn't even sending?

raw hill
#

If you want to write it as scratch work, go ahead

#

But I’m not going to continue parroting back the same answer to you

raw hill
#

Probably going to be with factorials based on what they sent earlier

#

Which is fundamentally the same thing

#

You just “bunch” all the terms together before cancelling

hoary iris
#

ye

#

anyways, we can bunch the terms and cancel it in scractch work

#

there my problem done lmao

#

Thank you for you help! @raw hill and @willow bear

#

shubham I'll wait for your idea

#

ping me once you're done

modest bolt
#

Π(k=m→n) (k+l) = (n+l)!/(m+l-1)!

Π(k=2→n) (k+2) = (n+2)!/(2+2-1)! = (n+2)!/3!

You can rewrite others like this and see the whole product= (n+2)/3n

hoary iris
#

I want to say you something bro

#

You have a great ideas to explain

#

please latex them bruh

modest bolt
#

ok wait

hoary iris
#

not now

#

I'll read this now

#

from next

#

How the hell?

hexed mulch
#

wsp

hoary iris
#

gpt??

hexed mulch
#

I just joined

#

✌️

hoary iris
hexed mulch
#

Nah I HIGHkey like maths

hoary iris
#

Everyone does that before coming here lmao

hoary iris
#

but they would lost their hope

#

here

#

but dw

#

get help from shubham

#

lmao

hexed mulch
#

I'm 12 btw, so no weird shi 🙏

willow bear
hexed mulch
#

However I am pretty good in maths

#

Just solved the 4d gaussian integral :)

willow bear
#

you're not allowed to be on discord if you're under 13, sorry mate

hexed mulch
#

I am 13 in 2 weeks?

hoary iris
#

ban him lol

hexed mulch
#
  1. WEEKS
willow bear
#

dunno this is up to the mods

hoary iris
hexed mulch
#

I just joined 😭

hoary iris
#

You'll be muted for 2 weeks lmao

hexed mulch
#

are we deadess

hoary iris
hexed mulch
#

yes it was:
pi^2

lyric meadow
#

sorry, we can’t have you if you’re under 13

hoary iris
#

sad @hexed mulch

#

bye for now

#

@lyric meadow Will you add him after 2 weeks?

lyric meadow
hoary iris
#

What a strict rule lol?

#

I wanna test him with integrals

#

btw

lyric meadow
#

it’s discord’s TOS

hoary iris
#

so sed

hoary iris
#

What if he lied that it is in two weeks?

modest bolt
#

did it

#

in latex

hoary iris
#

It is clearly not latex

#

lmao

hoary iris
#

after series of wrong results

modest bolt
#

it is i just pasted the latex in @obsidian monolith dm and uploaded the image here to not make it messy

lyric meadow
# hoary iris What if he lied that it is in two weeks?

we just want to make sure that there’s not people who we know/have reason to suspect are <= 12 that are on the server. if they claim to be 13 then we have no way of verifying this but this is at least in line with tos of not willingly allowing people who claim to be under that age on the server.

modest bolt
modest bolt
hoary iris
#

Thank you for your explanation, smay!

modest bolt
# modest bolt

if you think i copied the identity mentioned here from gpt, well i was making it here by using Π(k=1→n) k, what do you think i was typing for 10 mins blobwg

hoary iris
#

Also @lyric meadow If I claim to under 13 eventhough I am 16, Will you mute or ban me?

modest bolt
#

she will if you ping her 3 more times claiming the same

hoary iris
#

You've got brain to derive identities

modest bolt
#

mb

willow bear
hoary iris
#

lol

#

You sure don't like mispronouncing lol

lyric meadow
hoary iris
#

Don't ban me lmao

#

I am 16

modest bolt
#

did you learn Π from your classes or online?

hoary iris
#

my own little brain

#

understood

modest bolt
#

good 👍 me too 😂

hoary iris
#

it

#

It is easier than sum

#

I mean sigma

#

lmao