#help-23

1 messages · Page 416 of 1

gentle hedge
#

it's unituitive imo and it's not rigorous

calm cloak
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how about using L'Hôpital's rule

gentle hedge
#

some additional context is this is an exam question

frigid locust
#

try rewriting that to lnh / (1/h^2) and then read the logic they used

gentle hedge
#

and this part of the question is probably worht like

plucky elk
#

Why not

gentle hedge
#

2-3 marks

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so i want a method that takes 2-3 minutes

calm cloak
flat frigateBOT
#

| caesar |

gentle hedge
calm cloak
#

if you really wanna calculate the limit like this

gentle hedge
#

oh fair

#

that works i think

#

tysm

calm cloak
safe radishBOT
# gentle hedge tysm

If you are done with this channel, please mark your problem as solved by typing .close

gentle hedge
#

.close

safe radishBOT
#
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safe radishBOT
#
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errant parcel
simple gazelle
#

the basis vectors

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let me draw sum

errant parcel
#

ok, for your reference i have no background in linear algebra whatsoever

arctic raven
#

i is 1 step in positive x direction, j in y direction, k in z

errant parcel
#

this is my first time learning it

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oh

#

so i is a unit vector in positive x, and j and z is that?

#

basically just converting the scalars to vectors along those axis right

arctic raven
#

or if you like, $\mathbf i=(1,0,0),\mathbf j=(0,1,0),\mathbf k=(0,0,1)$

flat frigateBOT
simple gazelle
#

prob fucked up the coloring scheme

errant parcel
#

ok ok

#

got it guys

#

thank you

#

so how do i close this

simple gazelle
#

do .close

#

or sum

arctic raven
#

you type .close

errant parcel
#

.close

safe radishBOT
#
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simple gazelle
#

also remember that every vector is defined using basis vectors

safe radishBOT
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gentle hedge
#

is it possible to do this question as is or is there a typo for the P(Y=y) function

gentle hedge
#

they're independent

scenic dove
#

there's not really a question in that screenshot is there

gentle hedge
#

mb

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i dont want help with the question

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i just need to know

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if there's a typo

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or if thats the actual probability fucntion

scenic dove
#

oh it should probably be y=2,3,6 instead

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rather than x=

gentle hedge
#

ok ok

#

ty

#

.close

safe radishBOT
#
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#
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lapis token
#

I have a subset A of the real numbers where the elements are labeled using two different indexes from index sets
The sets are called I and J
My subset elements are labeled a_i,j

How do I interpret this subset and how do I prove this statement

lapis token
opaque fern
lapis token
#

I thought of it as a table with I for the columns and J for the rows

opaque fern
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so the middle part is the supremum of the row supremems

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and the right part is the supremum of the column supremums

opaque fern
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,, A = {a_{i,j}\where i\in \mathcal I, j \in \mathcal J}

flat frigateBOT
lapis token
opaque fern
lapis token
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Isn’t there one supremum for the columns and one for the rows

opaque fern
#

no

split kayak
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I got baited so fucking hard mb

opaque fern
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I mean there are ones for each row

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And one for every column

lapis token
opaque fern
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Its like

#

If you have a matrix

[
[1, 5, 3],
[2, 4, 8]
]

You can consider maximums across each row and column individually

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So if you srr considering it across the rows your set would be {5, 8}

lapis token
lapis token
#

I think I get that part

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Now we have a table

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And a bunch of sups

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What do we do from there

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The order seems to be irrelevant
Whether we search horizontally or vertically first

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But “just do whatever it’ll be fine“ doesn’t go well with math homework

safe radishBOT
#

@lapis token Has your question been resolved?

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safe radishBOT
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graceful lichen
safe radishBOT
graceful lichen
#

How coordinates of Q' is x1 - y1

#

or is it x1,y1 but mis printed in the book

tardy mango
# graceful lichen

Double ordinates are perpendicular to the axis of the parabola. The axis of the parabola is the $x$-axis, so $QQ'$ is a segment that is perpendicular to the $x$-axis. This means that $Q$ and $Q'$ have the same $x$-coordinate. Since the parabola is symmetric across the $x$-axis, we know that $Q$ being on the curve $\implies$ its reflection across the $x$-axis is also on the curve. And of course, reflecting over the $x$-axis negates the $y$ coordinate, giving $Q'=(x_1,-y_1)$.

flat frigateBOT
#

Civil Service Pigeon

graceful lichen
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oh okay

#

thats the thing

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in book if you see there is not comma

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nvm its clear

tardy mango
safe radishBOT
#

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graceful lichen
#

also

#

which formula they used to find trisection?

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of R and T

tardy mango
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Is that not just the section formula?

graceful lichen
#

mb i forgot that fr

tardy mango
#

bearlain rip

graceful lichen
#

didn't look at it in a while

safe radishBOT
#

@graceful lichen Has your question been resolved?

safe radishBOT
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safe radishBOT
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crisp hull
safe radishBOT
crisp hull
#

no idea how to do these

#

ik how to graph linear and quadratic functions btw

#

those were prev questions n now they jumped onto this

calm cloak
long orchid
#

when plotting composed function

calm cloak
long orchid
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@calm cloak i don't agree

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it'll be 3x

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that does no help OP to graph its sqrt

calm cloak
crisp hull
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it gives me ysq = 3x

long orchid
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how is taht useful

crisp hull
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ye i dont get it

calm cloak
long orchid
#

plotting 3x is elementary, it's a line

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then how do you take the sqrt of that

calm cloak
long orchid
#

yeah, so square that

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3x

calm cloak
long orchid
#

yeah

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and then what ?

calm cloak
long orchid
crisp hull
#

wait so like first i draw a quadratic graph of y sq then a linear for 3x?

calm cloak
long orchid
#

yeah sure

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so you'll end up with a graph of y^2

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then what ?

#

how do you plot the blue one from here ?

calm cloak
#

but with x>0

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thats quite literally the blue line

long orchid
#

i'm sorry

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i was mistaken

calm cloak
crisp hull
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alright now pls tell me in simple words

#

its my first time doin sq root graphs

long orchid
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(yh mine too lol, it isn't taught like this here)

calm cloak
long orchid
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basically you have to plot the graph of x = 1/3 y^2

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so horizontally

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(which you know how to graph because it's a quadratic)

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and then just focus on the top bit

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and thta's it

calm cloak
crisp hull
calm cloak
crisp hull
calm cloak
crisp hull
calm cloak
crisp hull
calm cloak
crisp hull
#

ye

calm cloak
#

so you can plot it that right? but remember in the original question we had y=sqrt(3x)

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so x>0,y>0

safe radishBOT
#

@crisp hull Has your question been resolved?

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safe radishBOT
#

Please don't occupy multiple help channels.

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grizzled kindle
#

I dont get what does the polynomial refer to in the next question, can anyone help?

the question reads "find all roots of the polynomial and then split them into linear factors: Z^3 - 1"

grizzled kindle
#

is Z^3 -1 the polynomial or Z?

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and also isnt Z = a + bi?

stoic dune
#

z³ - 1 is a polynomial

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z is "a complex number".
We may choose to represent any complex number as a + bi

grizzled kindle
#

right

stoic dune
#

Note that re^(it) is also a good representation of a complex number

grizzled kindle
#

Not sure we learned that yet

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but also if i dont know what Z is how can i find its roots?

stoic dune
#

Fair enough! Yeah you probably want to use z = a + bi here

#

Z can be anything, it's a variable!

You plug it into the polynomial Z³ - 1 to get another complex number

The question is: for which values of Z do we get Z³ - 1 = 0

grizzled kindle
#

I think theres a confusion here on my side

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When im told to find the root of Z^3 - 1, is the meaning not square root?

stoic dune
#

No. The roots of a polynomial are the values for which Z³ - 1 = 0

grizzled kindle
#

ohh

stoic dune
#

You can take the square root of a complex number, so if the question is asking for square roots specifically, we can talk about that too

grizzled kindle
#

No, im pretty sure thats what they mean.

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But the thing is, i could expand Z using a + bi and compare it to 0 but i vaguely remember another way to do it

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is comparing to 0 the right way?

stoic dune
#

There's a bunch of ways to do this problem! Expanding Z could work, but there's an easier way here

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Know any tricks for factoring Z³ - 1?

grizzled kindle
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I remember one method but i forgot its name

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not sure if its for roots or like nth roots

grizzled kindle
#

WAIT i think i remember

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Sorry for the wait im trying something

stoic dune
#

All good! lmk if you need any help with it. Good luck!

grizzled kindle
#

Alrighty i think i know how to do this but i messed something up :<

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i wrote the equation as Z^3 = i then i gotta turn "i" into its polar form

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so R = 1 (sqrt(0 + 1)) and Theta = arctan(0) = 0

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@stoic dune What am i missing in converting the imaginary number to polar form?

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i actually got it, thx!

#

.close

safe radishBOT
#
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balmy sparrow
#

Question: Prove that a zero vector 0 of a vector space V is unique.

Would someone be able to check over my proof, and let me know if its correct or if anything can be improved upon?

brave wolf
balmy sparrow
brave wolf
#

its basically that
01 + 02 = 01, because adding 02 doesnt change anything
but also
01 + 02 = 02, because adding 01 doesnt change anything

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so 01 = 01 + 02 = 02

balmy sparrow
#

Might be a stupid question, but how would I get into a position where I can say that 01+02, or that it equals either of the two? I understand the relationship. Is this just by definition of the zero vector again and instead of v we just do 01+02=02 or 01+02=01?

brave wolf
#

v + 0 = v holds for all vectors v, including v = 01 and v = 02

balmy sparrow
#

Gotcha. I appreciate you helping me out with this and checking over my work. Thank you!!

#

.close

safe radishBOT
#
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safe radishBOT
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fringe dock
safe radishBOT
fringe dock
#

regarding part b ii i am very confused

#

because i learnt that to find the range of values if it was concave is f'(x) < 0

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or where the graph is increasing/ decreasing

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now the worked solution has done f''(x) < 0

tardy mango
fringe dock
#

arent they literally the same thing

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because

#

concave/convex is just a graph that increases or decreases

karmic merlin
#

I think you should check out the definitions of concave in like your books or anywhere on the internet

fringe dock
#

dam

#

okay

fringe dock
# calm cloak

to show that a graph is increasing/ decreasing do we look at f'(x)

fringe dock
#

okay

#

thanks everyone

#

.solved

safe radishBOT
#
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shell mango
#

i hv a question

safe radishBOT
quiet plume
warm warren
#

!da2a

shell mango
#

lmfao okay it was a dare

safe radishBOT
#

Asking the actual question right away is more likely to get responses.

Asking "Can I ask...?" or "Does anyone know about...?" doesn't give people enough information to decide whether they can help, and answering can feel like a promise to help with the actual question, which they might find themselves unable to.

shell mango
warm warren
#

just .close

cunning spear
#

What?

warm warren
#

!done

safe radishBOT
#

If you are done with this channel, please mark your problem as solved by typing .close

shell mango
#

faaaaa

warm warren
#

look its either this or mods.

#

your choice.

golden nebula
#

Wtf is this

shell mango
#

okay sorry

#

mb mb

#

.close

safe radishBOT
#
Channel closed

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rare hound
#

No it fucking wasn’t a dare lmao

upper forge
#

Fr

rare hound
#

U did that all on ur own

rare hound
#

😭

#

But yeah bro did that willingly

upper forge
#

Tryna score baddies, when you need to score in exams

rare hound
#

@hollow canopy he did it

warm warren
#

Um its closed, can we stop.

golden nebula
#

Why are the mods serialised?

#

*sexualized?

thin bridge
#

These aren't things to "joke" about.

upbeat swan
golden nebula
#

Like the bot

shell mango
warm warren
golden nebula
#

The bot is a "she/they"

upbeat swan
#

Yes

golden nebula
#

And the other bot is a she/her i think

upbeat swan
#

It'a an attempt to spread awareness

golden nebula
#

But its not necessary is it?

warm warren
#

!redir

safe radishBOT
#

This channel is only for on-topic discussion. Please take casual conversation to #discussion or #chill.

thin bridge
stoic dune
#

It's not necessary to have a cookie, but I have a cookie anyway

hollow canopy
shell mango
#

i diodnt mean to do it that way , sorry , it wont repeat

warm warren
#

peoples, can we PLEASE STOP

upbeat swan
#

Ah course its nona

#

Btw Annie when did you get Helpful

hollow canopy
#

??

warm warren
upbeat swan
#

Yeah just noticed

#

Its cool

hollow canopy
rare hound
upbeat swan
#

You just seem like the type of person to do that

hollow canopy
rare hound
golden nebula
#

@warm warren getting so pissed looking at this

rare hound
warm warren
#

!redir

safe radishBOT
#

This channel is only for on-topic discussion. Please take casual conversation to #discussion or #chill.

warm warren
#

OR MODS

upbeat swan
hollow canopy
#

u started this btw

#

why were u talking about me like that

rare hound
warm warren
#

Can we all please stop and take this to #chill

upbeat swan
#

I didnt swear at you

#

You did

hollow canopy
#

tsk bye

rare hound
exotic anvil
#

what is going on

hollow canopy
#

talking to u is useless

rare hound
#

Nona didn’t do anything to u

proper cove
#

I genuinely cant tell whats going on here, so im going to ask you all just close the channel and move on

hollow canopy
#

And this is a help channel

#

Just leave

exotic anvil
#

the channel is closed

#

lets all take a step back

radiant isle
#

go to #chill and resolve it yourselves

lunar radish
#

Damn why does everybody named larp suck

radiant isle
#

these are called conflict resolution skills

upper forge
#

Wtf guys. Stop discussing in this channel. Ts closed

golden nebula
#

@warm warren finally got mods

rare hound
#

.close

upper forge
#

Lock the channel mods

exotic anvil
#

okay I will start muting ppl shortly

radiant isle
#

its already closed

upper forge
golden nebula
#

Wait i have a genuine question

thin bridge
#

Going to start dishing out mutes to anyone that still sends messages 2 minutes from now

rare hound
upper forge
#

Not close

golden nebula
#

How do you get the role that does nothing?

radiant isle
thin bridge
#

.remindme 2minutes

safe radishBOT
upper forge
exotic anvil
#

shhhhh

golden nebula
#

How do you get the role that does nothing?

exotic anvil
safe radishBOT
safe radishBOT
#
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safe radishBOT
stray crown
#

.close

safe radishBOT
#
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safe radishBOT
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stray crown
#

ok i actually need help

safe radishBOT
stray crown
#

<@&286206848099549185>

outer path
#

For the rhombus, you also need to show that opposite sides are equal since we are trying to prove that the shape is a rhombus

stray crown
#

wait

#

wrong image

#

sorry

outer path
#

From here I think you can state something similar to the sides, just that opposite angles are going to be congruent as well since it is a parallellogram.

#

After that, since opposite sides are congruent and opposite angles are congruent, that should be enough evidence to conclude that you have a rhombus.

stray crown
#

it says that i need to prove AB = BC

#

@outer path

outer path
#

True, since all 4 sides need to be the same.

#

I am writing it out now. I will come back when I have a better solution

stray crown
#

thank you

outer path
#

You should be able to prove that triange DEC is congruent to triangle BCE

#

THat would then prove that DC = BC

#

That would also really be the only reason we needed to know that CE is a bisector is so we can use that angle in some way.

#

Also, Knowing that <ADE is congruent to <ABE & <ABC is congruent to <ADC, this means that <CDE is congruent to <CBE
That means you have enough info for AAS triangle congruency (CE = CE)
From there it is enough evidence to state that DC= BC.

stray crown
#

alright thanks

#

.close

safe radishBOT
#
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lusty spear
#

I don't know what to do with this exercise, can someone help?
The task is to find for U_1 the so called "annulator" (U_1)^0.
So for a subspace U of V this U^0 is defined as shown ("für alle" = "for all")
lin(...) is the same as span(...)

Idk if this is common notation: V* is the set of all linear maps from V to the field F over which V is a vectorspace.

So for any f in (U_1)^0
0 = f( a (1 2) + b (4 3)) = a f(1 2) + b f(4 3)

Now I don't see how I could be any more specific about f

lusty spear
#

So I feel like I should treat f just as a "regular" vector conceptually

#

and formulate a basis

#

but idk cant really put the pieces together in my head

stoic dune
#

That's exactly it. What do you need me here for lol

lusty spear
#

Idk

stoic dune
#

One way we can discuss elements of V* is with row vectors. For example, [1 0] will multiply (4 3) and give back 4

lusty spear
#

I was confused as to how to do this

stoic dune
#

Where I'll use [] for a row vector, why not

#

Actually, even before that, there's easier useful details we can iron out. What's the dimension of U^0 here?

lusty spear
#

that is a good question

#

which I need to think about for a second

#

my gut feeling tells me it should be dim(U)

#

but no real argument

#

that I can think of rn

lusty spear
stoic dune
#

You don't NEED to represent these with row vectors, but it's a pretty natural choice.
I chose [1 0] just as an example, I could have also chose [2 2]

#

[2 2] acts on (4 3) by doing 2*4 + 2*3 = 14

#

I am implying with this choice that the set of all linear functionals on R^2 is a vector space with dimension 2. Which, it is

#

However some don't map U1 to 0, so the space we're looking for must have lower than dim 2

lusty spear
#

ok makes sense to me

stoic dune
#

Actually, an easier question I could have asked first, what's the dimension of U1 itself?

lusty spear
#

didnt check whether the two vectors a linearly independent

#

but I'd say they are

#

so 2

stoic dune
#

They definitely are! U1 is just R2 itself

lusty spear
#

ok I can see that

#

with (0 1) and (1 0) we can generate this basis

stoic dune
#

We can figure this out mechanically by multiplying
[a b] (any choice of vector) = 0

For two choices of vectors

lusty spear
#

wait if I remember correctly

#

if U is subspace of V and dim U = dim V then U = V ?

#

yeah I am pretty sure this is true

#

we have an isomorphism from V to F and from F to U

#

wait

#

oh ok I think it should make sense since U is subspace of V

#

anyways

stoic dune
lusty spear
#

for (1 2) I'd have 2(0 1) + 1(1 0)

#

for (4 3) it is 3(0 1) + 4(1 0)

#

actually should I not want to generate (0 1) and (1 0) from (1 2) and (4 3)?

#

so the other way around

stoic dune
#

[1 2] (0 1) = 2
[4 3] (1 0) = 4
You can think of these like a dot product. The important part is they map a vector to a real number

lusty spear
#

because obviously I can generate any v in R^2 from the canonical basis

lusty spear
#

I understand the computation

#

but not why

stoic dune
#

The thing you want to find now, is an a,b such that:
[a b] (any vector in U1) = 0

#

We can actually solve this as a system of equations by choosing two vectors to plug in. You had a good idea with (1 0) and (0 1)

lusty spear
#

ah ok I think I get it now somehow

#

because

#

I was also thinking about the system of linear equations thing

#

but I didnt really know how to do it

#

ok so I will try it again from here

#

thanks a lot!

stoic dune
#

Okay! Feel free to ask if you'd like any help with it

lusty spear
#

.close

safe radishBOT
#
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spiral saddle
safe radishBOT
spiral saddle
quiet plume
#

So what's your feeling about a) after those few examples you computed? (Note that you've only shown that 4 doesn't satisfy a), not that composites don't satisfy a), although the argument is similar).

Do you think it's a definition of prime numbers? In other words, do you think it is it true that a natural p satisfies a) iff p is prime?

  • If so, can you prove it?
  • If not, can you provide an example that exhibits that it's not the case?
quiet plume
#

Can you answer those questions?

quiet plume
#

Well you've tested two primes and they seem to satisfy a), and you've tested a composite and it doesn't seem to satisfy a).
Do you suppose that it's a definition of prime numbers or not?

spiral saddle
#

sometimes a conjecture works for some examples but not in general

#

is hard to tell really

spiral saddle
quiet plume
spiral saddle
#

you understand?

quiet plume
spiral saddle
#

I tried multiple possible values for p, being prime and composite

#

im not sure

#

should I have done only cases when p is prime and avoid p composite? @quiet plume

quiet plume
#

I am asking you specifically for p = 4. Does the fact that a) does not hold for p=4 mean that "p satisfies (a) iff p is prime" is false?

spiral saddle
#

unsure

#

care to give a hint

quiet plume
#

"p satisfies (a) iff p is prime" is the same as

  • if p is prime, then p satisfies (a), and
  • if p satisfies (a), then p is prime.
    Things that would invalidate this are : an example of a prime number which does not satisfy (a), OR an example of a number which satisfies (a) but is not prime.

Does the fact that 4 does not satisfy (a) fall into one of those two cases?

#

Similarly, does the fact that 2 satisfies (a) fall into one of those two cases?

#

And does the fact that 3 satisfies (a) fall into one of those two cases?

spiral saddle
#

those two cases

quiet plume
#

Then you've tried three numbers and have failed to produce a counterexample. You can either keep trying to find more in hopes of finding a counterexample, or try to prove that the statement is actually true at this point.

spiral saddle
#

because it might be just luck that any p in that range works but p outside that range doesnt @quiet plume

quiet plume
#

If you try to prove it and realize it doesn't work, then chances are you'll be in a better position to go back to the drawing board and pick a relevant counterexample.

spiral saddle
#

ok how to prove

quiet plume
#

What do you want to prove?

trim mauve
#

can anyone help me please

quiet plume
spiral saddle
quiet plume
#

What is the statement you're trying to prove explicitly? (What does it mean that a) is a characterization of prime numbers?)

quiet plume
#

It doesn't change what I'm asking. What is the statement you're trying to prove explicitly? It's a double implication.

spiral saddle
#

its an if and only if

#

@quiet plume

quiet plume
#

a) holds for p <=> p is prime

spiral saddle
#

or is it composite?

#

@quiet plume

spiral saddle
quiet plume
#

You're trying to show that a number is prime iff it satisfies a).

#

If you assume p is prime of course p is prime.

spiral saddle
quiet plume
#

What have you done so far?

spiral saddle
quiet plume
#

Ok, and how far along are you with the left direction? (I assume you mean proving that if p is prime then it satisfies a)?)

spiral saddle
#

I want to prove that if a) => p is prime

quiet plume
#

Ok.

#

Since p satisfies a), what divisors does p have?

#

Or rather, what does a) say about the divisors of p which are less than p?

spiral saddle
#

a) is forall d in N, (d < p and d | p) => d = 1

safe radishBOT
#

@spiral saddle Has your question been resolved?

#
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elfin pawn
#

Hey

safe radishBOT
elfin pawn
#

I need help

plucky elk
plucky elk
elfin pawn
#

I’m try to solve it first

#

Should be easy

clever tinsel
elfin pawn
#

The answer is 70?

grand basin
#

yeah

#

howd you know?

elfin pawn
#

Because it’s pretty simple I just need someone to double check my work if that’s cool

#

For this I got 62

grand basin
#

howd you figure that

elfin pawn
#

Because I read it ?

grand basin
#

Read it where?

elfin pawn
#

Bro

vague phoenix
#

Yes that is correct

elfin pawn
#

Can u just tell me if im wrong or correct so I can correct my answer

elfin pawn
#

For this I got A

#

4.1 and -2.2

grand basin
#

Right

rotund epoch
elfin pawn
#

Thanks

#

I got 90

vague phoenix
#

How come?

rotund epoch
#

?

vague phoenix
#

Note the word "average"

elfin pawn
#

Did I get it incorrect?

rotund epoch
#

-# I think it would be a range(average), like the B grade - 80-89

elfin pawn
#

O

#

So like

#

I grab the scores and see what’s the average

#

Oh yea your right

#

Let me re do it

#

So this is what

#

Add the scores: 89 + 73 + 75 + 83 + 72 + 78 = 470
Divide by 6 → 470 ÷ 6 = 78.3

So your average is 78.3%

#

That’s the grade

#

And I need __ to reach 80

#

Are sure it’s not 90?

rotund epoch
#

Not 90

elfin pawn
#

O

#

What is it then???

#

I’m so lost

#

Did u get the answer?

elfin pawn
#

Wait whatttt

rotund epoch
#

since you need at least an 80 for a B

elfin pawn
#

Yeaa

rotund epoch
#

If 78.3 is your score

#

and you need at least an 80

#

boom

elfin pawn
#

To get 80%

#

Not 90?

#

So the answer is 80?

rotund epoch
#

It does not say to get an A//next grade up? Unless there is more to that question

elfin pawn
#

Well I feel like 80 is not going to bring up your grade by 2 percent

#

I have 2 attempts I’ll let you know if your right

#

Can you help me on this?

#

I got -15.9

#

No change that I got -17.4

rotund epoch
# elfin pawn Not 90?

on a second thought, it might be 90, because you need
89 + 73 + 75 + 83 + 72 + 78 = 470
with 78.3 as the mean
and to make the mean a 90,
(89 + 73 + 75 + 83 + 72 + 78 +** 90**) / 7
~_~ sorry!

elfin pawn
#

Noooo it’s totally fine

#

It’s okay

elfin pawn
#

I’m not the brightest at math

prisma wren
# elfin pawn

Try to write out the mean as an expression of the known numbers, and the missing one

elfin pawn
#

Did I get it incorrect stitches ?

#

I got -17.4

rotund epoch
rotund epoch
elfin pawn
#

Oh yeaaa thanks

#

30.9?

prisma wren
#

show work

elfin pawn
#

I only have to show work for the last questions

#

Like 2 of dem

rotund epoch
#

-# Still, good habit + it will help us help you

prisma wren
#

presumably you got your answer of 30.9 by doing some work. show that work so we can verify/tell you where you went wrong (if you did)

#

unless 30.9 fell to you from the heavens

elfin pawn
#

LOL

#

Sure

#

I’m

#

My hand writing is pretty bad

#

If u don’t mind

#

Skipped some steps Becuase I can do some in my head

rotund epoch
#

You only used 3 of the initial digits, the last 2 weren't subtracted from the mean cat_crySob I guess I was wrong again

#

And were not squared

prisma wren
#

Yes, 30.9 is correct, assuming population. presumably you used symmetry for 11

elfin pawn
#

Kk

#

Thanks so much

#

I’ll Make it easier for u guys to read for the next question

#

Just give me a second to finish this

#

The boxed is my answer

#

This is for part a

#

Sorry my hand writing is so baddd

#

My first language is Arabic so bear with me

rotund epoch
elfin pawn
rotund epoch
elfin pawn
#

So I submitted it

#

And the only wrong answer I got

#

Was the 30.9

#

Can we do that one again?

rotund epoch
#

I thought so..

elfin pawn
#

Yea I don’t know where I went wrong

#

Stitches said it was right

#

But it’s my fault

rotund epoch
#

Did it say the answer?

#

for a sample, it would have been 37.1

elfin pawn
#

Noo sadly it didn’t say the answer

#

Let me try to solve it again

#

Yes I think it is 37.1

#

Just give me a second

rotund epoch
#

you do

|| Just like the steps of standard deviation ----> (1 - 7.5)^2 + (4- 7.5)^2+ (5- 7.5)^2+ (6- 7.5)^2+ (11- 7.5)^2+ (18- 7.5)^2||
||OVER||
||The amount of data ---> 6 minus 1||
||185.5/5||
= ||final answer of 37.1||
and that is the variance for the sample

safe radishBOT
#

@elfin pawn Has your question been resolved?

safe radishBOT
#
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worldly lantern
safe radishBOT
worldly lantern
#

why is this legal

prisma wren
#

Be more specific. (ii) in your photo is sort of like the chain rule https://en.wikipedia.org/wiki/Chain_rule . Implicit differentiation works cause of the chain rule being implicitly applied when necessary.

In calculus, the chain rule is a formula that expresses the derivative of the composition of two differentiable functions z and y in terms of the derivatives of z and y. More precisely, if

    h
    =
    z
    ∘
    y
  

{\displaystyle h=z\circ y}

is the composition such that

 ...
#

That (-) shouldnt be there

worldly lantern
#

its not chain rule

#

its just

#

differentiation of implicit function

#

let f(x,y) be given
now to find dy/dx we do partial derivative of f(x,y) wrt x and wrt y

#

this is what i mean

golden nebula
#

I don't think this formula is correct

#

Oh wait never mind

#

While not being the best explanation, I assume that its because every term that has a "dy/dx" must have a differentiated function with respect to y along with it. Everything without dy/dx is either a constant or is a differentiated function of x. Also, for a product of a function of y and a function of x, it splits into 2 (by product rule I think, I always forget the rule name). This is the best explanation I can do. If you want a clearer explanation, you can try googling or waiting for someone else to respond

median vigil
# worldly lantern

you can't just ``cancel'' the $\partial f$s the way you would with ordinary derivatives

flat frigateBOT
#

clôud

golden nebula
median vigil
#

well you have to approach it from the multivariable chain rule

#

if you have a curve $f(x,y) = C$ and you differentiate in such a way that $y = g(x)$ is an implicit function defined by that curve, then you essentially differentiate ``along the curve'', so since $f(x,y)$ is constant along the curve:
[
\odv fx = \pdv fx + \pdv fy \odv yx = 0 ]
then just rearrange for $\odv yx$

flat frigateBOT
#

clôud

worldly lantern
#

damn

#

thanks

#

.close

safe radishBOT
#
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safe radishBOT
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honest peak
#

How do I proceed from here, I know it must convert into an integral but how

left gyro
honest peak
#

Nope
But I know limits of a sum

left gyro
#

riemann sums look like:

#

,,\lim_{n\to\infty}\sum_{k=1}^n\frac1nf(\lambda)=\int_0^1f(\lambda)d\lambda

flat frigateBOT
left gyro
#

also, k isn defined when you move it outside of the ∑

honest peak
#

Oh
But how is 1/n = dλ

left gyro
#

its not a literal limit

left gyro
#

you cant just replace a ∑ with a ∫

left gyro
#

the idea for this is partly due to what an integral is

#

have you done integrals before?

honest peak
left gyro
#

what do integrals look like, on a graph?

honest peak
#

Summing slivers to get area under the curve

#

Ohhh

#

I get it

left gyro
#

this I think is partly the definition of such an integral

#

rigorously it can boil down to this, for continuous functions at least

honest peak
#

1/n can be thought of as a nudge in the x, a dx

left gyro
#

youre not using the word nudge correctly
nudge = movement

#

here, 1/n is the width of the rectangle instead

#

1/n width, f(k/n) height

honest peak
#

Got it

#

Thanks!

left gyro
#

np

honest peak
#

.close

safe radishBOT
#
Channel closed

Closed by @honest peak

Use .reopen if this was a mistake.

left gyro
#

I still need to check your work though

#

nvm there isnt anything wrong with it other than moving that k out

meager ravine
#

@plush ravine please help me w my maths hw😔

#

@plush ravine

safe radishBOT
#
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craggy tree
#

question: why does g(x) = x|x| at x = 0 not serve as a counterexample to (c)?

craggy tree
#

oh wait i misinterpreted "all its derivatives exist" as "its first derivative exists at all points"

#

oops

#

ok nevermind

#

.close

safe radishBOT
#
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burnt nymph
#

3x²+2√6+2 find roots

safe radishBOT
normal moss
normal moss
#

$3x^2 + 2\sqrt{6} + 2 = 0$

flat frigateBOT
normal moss
#

This is a quadratic in the form $ax^2 + c = 0$

flat frigateBOT
normal moss
#

c is 2sqrt(6) + 2

burnt nymph
#

Yes

normal moss
#

There's no bx, linear term

#

Okay

burnt nymph
#

ax²+bx+c

normal moss
#

Yes

#

But there's no bx

#

That's why I am asking

burnt nymph
#

Oh wair

normal moss
#

If it's supposed to be that

burnt nymph
#

Wait*

normal moss
#

Or is there an x missing

#

At 2sqrt(6)

burnt nymph
#

It's 2√6x

normal moss
#

Right

#

$3x^2 + 2\sqrt{6}x + 2 = 0$

flat frigateBOT
burnt nymph
#

Yeah

normal moss
#

Anyway

#

!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
burnt nymph
#

2

normal moss
#

Can I see your work

burnt nymph
#

First i thought a lot that how to split 2√6x but I couldn't find it

#

Then I did
(√3x+√2)²

normal moss
#

Are you supposed to solve by factoring?

burnt nymph
normal moss
#

Yes, that's factoring

#

Though in this case it can be slightly tricky to find it

#

Though you did

#

Correctly

#

$\left(\sqrt{3}x + \sqrt{2}\right)^2 = 0$

flat frigateBOT
normal moss
#

Now what

burnt nymph
#

To get zeros

normal moss
#

How

burnt nymph
#

Idk that's why I came here

normal moss
#

I see

#

Well

#

We have an equation in the form of

#

m^2 = 0

#

When would this be 0

burnt nymph
#

√3x=√-2

#

X=√-2/√3

normal moss
#

Uh

#

Not exactly

burnt nymph
#

Then rationalisation

#

?

normal moss
#

Why minus inside the sqrt

burnt nymph
#

-√2

normal moss
#

Yes

#

When moving, you change the sign of the entire expression

#

sqrt(2) is the expression here

burnt nymph
#

-√6/3

normal moss
#

Hence - sqrt(2)

burnt nymph
#

Root

normal moss
#

Yes

burnt nymph
#

But there is only one root

normal moss
#

Yes

burnt nymph
#

But it's a quadratic

normal moss
#

Well technically

#

It's not one root

#

There's 2

#

But they are the same

normal moss
#

It's squared

#

That means the root repeats

#

Because you can write the square as a product right

burnt nymph
#

Oh ok

normal moss
#

And you get the same root from both factors

#

Have you learned about the discriminant yet?

burnt nymph
#

No

normal moss
#

Oops

#

Auto correct

burnt nymph
#

What is discriminant

#

Btw

#

I have one more question

normal moss
#

Well it tells you what kind of solutions the quadratic equation has

#

Simply put

#

Sure

#

If it's positive, there's 2 unique real solutions. If it's negative, there 2 unique complex solutions (conjugates). If it's 0, there's 1 repeated root

burnt nymph
#

6x²-7x-3 find alpha⁶+beta⁶ and 1/alpha³+1/beta³

normal moss
#

Here the discriminant is 0

bitter sparrow
normal moss
#

There's 2 ways of doing this

#

You can find alpha and beta and compute

burnt nymph
#

Using identity

normal moss
#

Which here is simple

#

Otherwise

#

You need to know a bit about a^6 + b^6

bitter sparrow
#

Lmao why complicate it so much

burnt nymph
#

. close

#

.close

clever tinsel
#

no spaces.

safe radishBOT
#
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normal moss
#

Saying "thank you", or "bye" at least is really not that difficult

#

😒

near sky
#

Have a nice day

astral glacier
#

-# now kiss

near sky
#

Kiss xavier

safe radishBOT
#
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merry lintel
#

I have 2 uhh functions?
$$f(t) = 5900 * 1.002^t$$
And
$$g(t) = 8000 * 1.012^t$$
f(t) is rent
g(t) is salary
The time unit is months
The question is
After how many months will the rent be 60 percent of the salary?

flat frigateBOT
main mural
#

it's \% for percentage signs in latex fyi catthumbsup

merry lintel
#

i see
thanks :)

main mural
#

or actually where are you stuck

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
merry lintel
#

I found it to be 9833.33

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60% of that is 5900 i think

main mural
#

can you show your steps

merry lintel
#

one sec

#

I tried drawing it but
typing was faster so

buoyant shadow
#

just write the correct equation

#

literally

#

you;re thinking too much

merry lintel
#

whats the correct equation

main mural
#

you threw away the exponential information

merry lintel
#

I tried 9833.33 = 8000 * 1.012^t

main mural
#

just solve $f(t) = 0.6 \cdot g(t)$

flat frigateBOT
#

artemetra

buoyant shadow
#

5900 * 1.002^t rent
= is
0.6 (8000 * 1.012^t ) sixty percent of the salary

merry lintel
#

oh

#

I see

#

thanks for the help :)
thats it

buoyant shadow
#

sorry made a mistake

merry lintel
#

all good

#

thank you both

main mural
merry lintel
#

.close

safe radishBOT
#
Channel closed

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safe radishBOT
#
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near sky
safe radishBOT
karmic merlin
#

What have you tried so far?

near sky
#

so we were doing this yesterday,
with angle AMC = 90, M is on a sphere with diameter AC
A point K on plane perpendicular to AB forms 90 angle for ABK so M lies on that plane too, locus is the intersection of the plane with the sphere

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AM traces a cone like shape

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@naive dragon

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nvm

#

<@&286206848099549185>

fleet willow
#

!15m

safe radishBOT
#

Please only use the <@&286206848099549185> ping once if your question has not been answered for 15 minutes. Please do not ping or DM individual users about your question.

near sky
fleet willow
#

since someone last answered

near sky
#

but i get it

safe radishBOT
#

@near sky Has your question been resolved?

gaunt elk
#

Let's define coordinates of $N$ : $(x_N,y_N,z_N)$.
Can you find an equation verified by those coordinates ?

flat frigateBOT
#

Lin Xia

fair hound
#

I think there is a problem with the exercise, you might have miswrote something

#

this lead to a problem of definition for M

gaunt elk
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why ?

fair hound
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can't find such a point M, this def implies M is on the sphere of diameter AC and M is on the plane going through B and perpendicular to (AB)

gaunt elk
#

yes there re several solutions

fair hound
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there aren't

gaunt elk
#

it's aa circle

fair hound
#

good luck to find a circle consisting of 0 point

near sky
#

oh

gaunt elk
#

hum you mean with those coordinates

near sky
#

must AMB then

naive dragon
#

someone insert heisenberg gif pls

naive dragon
#

there are no such M

gaunt elk
#

unlucky

naive dragon
#

ty for trying that problem xD

near sky
#

:)

naive dragon
#

Actually someone said it does not exist but I just kinda, ehhh anyway

#

It's still a fun problem

near sky
#

yes

#

ty

fair hound
near sky
#

.close

safe radishBOT
#
Channel closed

Closed by @near sky

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safe radishBOT
#
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timber karma
#

Let $\ell$ be a line in the plane, and $90^{\circ} < \theta < 180^{\circ}$. Consider any three distinct points $P,Q,R$ satisfying the following: $\ i) P$ lies on $\ell$ and $PQ$ is perpendicular to $\ell \ ii) R$ is on the same side as $Q$ relative to $\ell$, but not on $\ell$. $\ iii)$ For any $A,B$ on $\ell$ such that $\angle ARB = \theta$, then $\angle AQB \geq \theta$. \ Determine the minimum of $\angle PQR$

flat frigateBOT
#

Copter

timber karma
#

I have something that looks like this

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but im kind of confused, cant we pick B=P and A large enough such that <ARP is theta, then <AQP is less than theta?

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or am i misinterpreting the question

golden nebula
#

If the question states that angle AQB is greater than or equal to theta, I assume that your take would be invalid

safe radishBOT
#

@timber karma Has your question been resolved?

timber karma
#

oh

#

why is it wrong then?

#

<@&286206848099549185>

golden nebula
#

It would be invalid because angle AQB would be less than theta

timber karma
#

well, couldnt i just pick the same thing regardless of where R is?

golden nebula
#

What do you mean?

timber karma
#

or am i trolling

golden nebula
#

If you pick B=P, then angle AQP is less than theta right? You said it yourself. So I think it might not me valid. Or I misunderstood the question

timber karma
#

but ARP is theta

golden nebula
#

Oh my bad. I meant that it would be invalid because theta is between 90 and 180. so if P coincides with B, theta woudl be less that 90

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Sorry for the confusion

timber karma
#

oh wait

#

yeah i see

#

sorry mb

golden nebula
#

Also @timber karma, I recall you sent something related to inversion related to a circle. What does that mean?

#

(This is completely unrelated to the current question btw)

timber karma
timber karma
#

.close

safe radishBOT
#
Channel closed

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safe radishBOT
#
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copper shadow
#

For 27 d I have that f(x)= x for 0<x<1 and for x>1 f(x)=e^x+c. How can I go about finding c? I know he gives f(0)=0. But e^x+c is for x>1 so I don't see how I can use both information in conjunction

copper shadow
#

Yes but I can just sub in x instead of logx

verbal cloud
#

yes

copper shadow
#

Sorry I'm not seeing why f(log) is important

verbal cloud
#

e^x+c is for x>1

so when x = 1 what happens

#

it's not f(1)

#

I think you should try to do the substitution formally

copper shadow
copper shadow
verbal cloud
#

not really since you want the function to be continuous, so both cases should handle it

verbal cloud
#

x > 1 iff u > ...

copper shadow
#

Oh wait

#

It is differentiable

verbal cloud
#

f is differentiable thus continuous

copper shadow
fathom jewel
verbal cloud
#

I think so

copper shadow
flat frigateBOT
#

BigBen

copper shadow
#

So multiple both sides by $\lim_{h\to0}h$

flat frigateBOT
#

BigBen

verbal cloud
copper shadow
verbal cloud
#

what isn't 0

copper shadow
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It isnt defined for 0

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Only for u>0

verbal cloud
#

well it's continuous so it's essentially the same

copper shadow
#

I'm not following

verbal cloud
#

if you take the limit as u goes to 0 you have the same equality as if it was defined at 0

fathom jewel
restive niche
#

no, its correct

#

a function being differentiable at a point means it is continuous there

#

although you could phrase your proof a bit better

copper shadow
copper shadow
copper shadow
#

Ok f(0)= 0 if x is 0 and f(0) =0 if e^x+c. So c=-1

verbal cloud
#

yep