#help-23

1 messages · Page 378 of 1

vale vessel
#

are you basically trying to prove that given (A -> Xk is safe), a new collision must occur in the path (Xk -> X{k+1})?

chilly plover
#

ok I think question 2 is true, I'll write some explanation

cosmic sparrow
#

i decided to run it and it SEEMS to work im still not sure

chilly plover
#

I take question 2 as:
if B and C are one A* step apart, then is any point on the line from A to C at most one A* step apart from the line from A to B?

The case where the lines are the furthest apart is when A is infinitely far away and the lines are almost parallel, so I will assume that the lines are simply parallel.

Let D be some point on the line from A to C.
Because the lines are parallel, there is a point on the line from A to B that is exactly one A* step apart from D. (the points have the same offset from the center of the tile)

So it is true for the parallel case, and in any other case, the lines are closer so it is true as well.

cosmic sparrow
#

i have no idea what your talking about but its 1 am

chilly plover
#

oh hmm

cosmic sparrow
#

if what you said is right then it proves what your seeing here? i tried to run it with this logic

chilly plover
#

If the "border strip" is all the tiles that are at most one A* step away from the line A to B, then the property is true. (I think this is the same as what I tried to say)

cosmic sparrow
#

what is a border strip and what is A* step away

chilly plover
#

You mentioned it here:
"one A* step in an 8-neighbor direction (up/down/left/right/diagonal by 1 tile)"
and "Is it true that the straight move from A to C can only touch new tiles in a small “border strip” on the side corresponding to the direction B\to C?"

#

A border strip is generally a line (strip) that is right next to (borders) something, in this case the line from A to B in the question.

cosmic sparrow
#

yes yes

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but what is A* step away?

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oh i understand i think

chilly plover
#

I don't know how to explain it besides how you described it at the moment

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for example if you are at the black circle, then all gray squares are one A* step away

cosmic sparrow
#

yes i get it now

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i just dont understand your proof its too complicated for me 😭

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especially D

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il try to get things straight its a bit late, can i get back to you later? i dont want to trouble you @chilly plover

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il check your proof tomorrow and get things straightened

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thanks

chilly plover
vale vessel
#

<@&268886789983436800> ? ^^

junior smelt
#

What the hell!?

dry sierra
#

What

wispy berry
#

okkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkkk

native cape
#

I got a question

#

It’s radicals

broken forum
#

what's bro's question?

safe radishBOT
#

@cosmic sparrow Has your question been resolved?

vale vessel
safe radishBOT
safe radishBOT
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river needle
safe radishBOT
river needle
#

for b.) how did they know f(2) is a minimum

clever gale
#

They differentiated f(x) and set it equal to zero in order to find the x-value of the extrema point

river needle
#

ik but that only tells u where the turning point is

#

it doesn't tell u whether the turning point is a minimum or maximum

open wedge
flat frigateBOT
#

1 divided by 0 equals Infinity

river needle
#

how does the second derivative tell me whether the value is a minimum or maximum/

charred summit
#

sub the x value where f'(x) = 0 into the second derivative

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if >0 the graph is concave up

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<0 concave down

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= 0 inconclusive

charred summit
charred summit
river needle
#

hmm this is a lot of work for a simple question that's worth 3 points only

river needle
#

p.s differentiating f(x) a second time is a pain in the neck

#

but i suppose there's no other way

charred summit
river needle
charred summit
#

oh you already sent it here

nimble vine
#

if allowed

river needle
#

nah not allowed in an exam

nimble vine
#

den no

river needle
#

damn

#

so u agree ts is bullshit?

charred summit
#

Calculating the second derivative for exercises like this is very usual tbf

river needle
#

for the record

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i dont think we've been taught that

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taking second derivative

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then pluggin in value

nimble vine
#

no wait

hallow swan
# open wedge hm

No!Division by zero does not exist because there is no number that, when multiplied by zero, results in the dividend. 2/0=0 0x0<>2

river needle
#

wrong channel i think

charred summit
#

You can also find all f'(x) = 0, which are all candidates for maxima or minima. Then choose values slightly less and slightly greater than those points to determine the sign of f'(x). Then you can interpret sign changes from positive -> negative will be a local maximum, negative -> positive local minimum

#

No sign change --> neither max or min

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But just taking the second derivative is easier imo^

river needle
#

alright thx

#

.closse

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.close

safe radishBOT
#
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round temple
#

Hi I was just wondering if anybody can do these math problems for me

round temple
#

I did a rough translation but and it may not be accurate but I hope it helps

charred summit
#

No one is going to do them for you

#

Someone will help you solve them though if you're having trouble doing so yourself

round temple
#

Well I kinda don't understand the whole subject so yeah

nimble vine
safe radishBOT
#

@round temple Has your question been resolved?

safe radishBOT
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oak dagger
#

Is my parabola correct? Why does it seem incomplete

shut storm
#

,rcw

flat frigateBOT
shut storm
#

you seem to not have taken any negative x-values. that's the only thing I can say

hollow dock
#

Parabola seems look ok

shut storm
#

and that is probably the reason it feels incomplete

#

but otherwise there's nothing inherently wrong with the parabola itself.

safe radishBOT
#

@oak dagger Has your question been resolved?

shut storm
#

react to the bot then. the bot cannot read text responses.

vagrant ice
safe radishBOT
#

@oak dagger Has your question been resolved?

safe radishBOT
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covert talon
safe radishBOT
covert talon
#

Rlly quick question

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The mark scheme said 2.2-2.21 so would i still get the mark or no

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Bc i basically did what the mark scheme said to do

vagrant ice
#

,w 1.6 / cos(42 deg)

covert talon
#

I got 2.15 bc rounded too early so

vagrant ice
covert talon
#

O

vagrant ice
#

yeah you should keep 1.6 to like 6 dp

burnt mantle
#

you wouldnt get the mark

covert talon
#

So next time just round at the end right

vagrant ice
#

just to be safe

covert talon
#

Oh okok

vagrant ice
#

exactly!

burnt mantle
#

you would get M1 but not A1

vagrant ice
#

don't round intermediate steps that much

covert talon
#

Okok

#

Thank u

vagrant ice
#

no worries

covert talon
#

.close

safe radishBOT
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covert talon
#

.reopen

safe radishBOT
covert talon
#

Nvm I’m back

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How do I o this I, rlly confused

vagrant ice
#

say 1 = n

how can you write 2 and 3 in terms of n?

covert talon
#

2n and 3n

vagrant ice
covert talon
#

5n

vagrant ice
covert talon
#

wut

#

o

#

ermm

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1 + n and 1 + 2n?

proud tree
#

well 2=(1+1)

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similarly, how would you write 3

covert talon
#

(2+1)

proud tree
# covert talon

for any general n, can you express the nth term in this sequence

covert talon
#

(n+1)?

proud tree
#

you know that you always divide by 2

#

let's look at the numerator for some terms

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for 3, it's (3)(4),
for 4 it's (4)(5),
for 5 it's (5)(6)

vagrant ice
proud tree
vagrant ice
#

so what you need is the next number after the next number

covert talon
#

ohhh yes

proud tree
#

so how would you express the nth term

covert talon
#

n(n+1)?

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wait

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erm

proud tree
#

don't forget the 2

vagrant ice
#

oh yeah you forgot to divide by 2

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yeah that's correct then

covert talon
#

n(n+1)/2

proud tree
#

👍

#

how would you express the (n+1)th term

covert talon
#

ohh

vagrant ice
#

yes, so that's correct for (number * next number)/2

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how about (next number * next next number)/2

covert talon
#

n(n+2)/2?

broken forum
#

close

proud tree
covert talon
#

is it just (n+2)

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/2

vagrant ice
proud tree
#

what would be the number after n?

covert talon
#

n+1(n+2)? idk

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auggh

proud tree
covert talon
#

oh so its

vagrant ice
#

there we go you have the right idea

covert talon
#

(n+1)(n+2)/2

proud tree
#

okay now add both the terms

vagrant ice
#

don't expand

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you have [ n(n + 1) + (n + 1)(n + 2) ] / 2 if you add both fractions

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which term is in common?

covert talon
#

the n+1 right

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(n+1)

vagrant ice
#

so you can factor n(n + 1) + (n + 1)(n + 2)

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(n + 1) * (...)

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a simpler example is something like $2 \cdot x + x \cdot 3 = x \cdot (2 + 3)$

flat frigateBOT
covert talon
#

so is that x(3 + 2) = x (2 + 3)

vagrant ice
#

$\cdot$ means 'multiply'

flat frigateBOT
broken forum
vagrant ice
#

yeah, factoring is the distributive law but you do it backwards

#

if you've ever seen a(b + c) = ab + ac but never realised what it means

#

what we're doing here is starting from ab + ca
= ab + ac
= a (b + c)

#

2 * x + x * 3
= x * 2 + x * 3
= x * (2 + 3)

covert talon
#

👍

proud tree
broken forum
covert talon
#

do u just

#

Foil it

vagrant ice
covert talon
#

Or does it become 2n(n+1) (n+2)?

#

o

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ok ok

covert talon
vagrant ice
#

yeah cause you just add n and (n + 2)

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okay so $\frac{(n + 1)(2n + 2)}{2}$

flat frigateBOT
vagrant ice
#

you can definitely simplify this

#

nearly there

proud tree
covert talon
#

the

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2?

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2(n+1)?

vagrant ice
#

yep!

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$\frac{(n + 1)2(n + 1)}{2}$

flat frigateBOT
covert talon
#

o

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Do u thenlike divide the exponent by the denominator

proud tree
#

exponent?

vagrant ice
#

that's not an exponent but yes

covert talon
#

the

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outside thing

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oops

proud tree
#

so what would be your final expression

covert talon
#

(n+1)(n+1)

proud tree
#

hmm

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what more could you do

covert talon
#

expand

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n^2 + 2n + 2

proud tree
#

you want to simplify it

proud tree
#

i mean the terms

covert talon
#

o

#

(n+1)^2

proud tree
#

👍

covert talon
#

ohh

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is that like the fina thiing i need to show then

proud tree
#

yep

covert talon
#

ohh

#

so annoying wtf and only for 4 marks 😭 legit all the harder higher mark ones r easier than this for me tbh

#

tysm tho

#

.close

safe radishBOT
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lament kiln
#

Do you know how to solve Raabe Duhamel or Mac Lauren?

safe radishBOT
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granite dove
#

we need to differentiate this expression wrt x
please help

fathom adder
#

Write it y = this

granite dove
#

yeah

stray yoke
#

You will get a differential equation

fathom adder
#

you will get y² - sin²(x) = y
2yy' - 2sin(x)cos(x) = y'

stray yoke
#

y = this
Then square both sides
Differentiate both sides wrt x
Solve the DE

granite dove
#

ohk got it... tysm

#

i'll just try and see if i get the ans

fathom adder
#

Assuming x belong to an interval where y is actually differentiable also

granite dove
#

yeah got it thank you so much !!

#

.close

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granite dove
#

.reopen

safe radishBOT
granite dove
#

I am sorry but I needed to ask one thing that how did you write that entire infinity series just as sin sq (x)

mighty mango
brave wolf
#

you could just do quadratic equation if u wanted to

mighty mango
#

square both sides

mighty mango
#

y^2 = sin(x)^2 + that infinite series which is just y again

granite dove
#

yeah but even if i square what about the rest of the roots in there

mighty mango
#

so y^2 = sin(x)^2 + y

jolly bridge
granite dove
#

ohh wait i think i get it now... yeah

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it's y all over again

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thank you so much everyone

jolly bridge
#

elligant

mighty mango
#

absoltely

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fuck

mighty mango
granite dove
#

.close

safe radishBOT
#
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jolly bridge
#

sure? about...

mighty mango
#

or.. nvm i can ask about the differential equation part in hlounge

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about the requiring differnetial equations

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bc you ?'ed

mighty mango
#

it is just an implicit function... no?

jolly bridge
#

.it doesnt

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yeah

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he just differentiated what you did

mighty mango
#

.oh- so why did you ? me 😭

jolly bridge
#

y^2= sin^2 x + y

mighty mango
jolly bridge
granite dove
#

Maye she meant Differential equation.. maybe she confused it with integration by any chance

mighty mango
jolly bridge
mighty mango
jolly bridge
mighty mango
#

.oh yeah i see

#

.alright ty!!!

safe radishBOT
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safe radishBOT
mighty mango
#

<@&268886789983436800>

#

check this amazing deal

safe radishBOT
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dusky echo
#

.close

mighty mango
# dusky echo .close

the channel is already closed. you also cant close other people's channels if they're claimed.

dusky echo
#

Sorry

mighty mango
dusky echo
#

nice pfp btw

#

are you using nitro?

mighty mango
#

or... some pink person might... banhammer us

#

well- not ban but warn

#

so lets avoid the hustle

#

and stay silent!!!

#

❤️

junior smelt
mighty mango
#

-# oh no!!!!! its a pink person!!!!!

mighty mango
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halcyon light
safe radishBOT
halcyon light
#

does my work look ok?

#

idk if I understood this right

light shoal
#

yes, 3/8 is correct, and your reasoning is correct

#

however you stated it wrong at the end:

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that probability of that event is 1/8

#

but that's only one of the three ways to get two heads and one tail

#

if you had said P(two heads and one tail) = 3/8, that would be correct

halcyon light
#

ohhh

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ok

#

thanks

light shoal
#

yw

halcyon light
#

What about this one? Is it rly this simple?

fathom adder
#

Yeah, whatever its tail or head they play a symetric role

halcyon light
#

.close

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steep magnet
safe radishBOT
steep magnet
#

I dont really understand what theyre saying in the solution here

#

I think this means the derivative is negative between 0 and 2pi

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But idk how they got that or what to do with this information

#

Wait I see now that tells us its a local max at 0 and min at 2pi

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But I still dont see how they got that its negative between 0 and 2pi

median vigil
#

if theta varies between 0 and 2pi, what interval is theta/2 over?

steep magnet
median vigil
#

like lower and upper bound

#

$0 \le \theta \le 2\pi$ therefore $? \le \frac{\theta}{2} \le ?$

flat frigateBOT
#

cloud ☁

steep magnet
#

Ohhhh

#

0 <= theta/2 <= pi

median vigil
#

yes

#

and if its input is between 0 and pi, is sin positive or negative?

steep magnet
#

Positive?

median vigil
#

yes

#

so if sin is positive then -3/2 sin is...

steep magnet
#

Negative

#

Ok makes sense, but how do we then know that it becomes positive when theta < 0 or theta > 2pi

median vigil
#

you can do a similar analysis

steep magnet
#

Ok I think I get it

#

Thank you!

#

❤️

#

.close

safe radishBOT
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acoustic zealot
#

matrix multiplication:
i have
A =
(1 # 2 # 2
1 # 2 # 1)

and B =
(1 # 2
3 # 1
1 # 1)

C = A * B; my solution: C=
(5 # 10
12 # 4)

I did
(B0,0 * (A0,0 + A0,1 + A0,2) # B00,1 * (A0,0 + A0,1 + A0,2)
B1,0 * (A1,0 + A1,1 + A1,2) # B1,1 * (A1,0 + A1,1 + A1,2))

is it correct?

peak estuary
#

no

#

the fact that you havent even used every entry of B should make you suspicious

acoustic zealot
#

ok, that s what i exepted, i did some of these tasks, and all of my solutions were wrong

#

i though it should result in a 2x2 matrix so, why should i use Bi,2

muted sapphire
#

well you have to get a 2x2 matrix

peak estuary
#

well you still used all entries of A

muted sapphire
#

and use all elements

peak estuary
#

why did you use that

#

with the same flawed logic you shouldnt need all entries of A either

acoustic zealot
#

wait, i think i got it, let me retry

#

i will send the solution

#

(25 # 20
20 # 16)

peak estuary
#

no

acoustic zealot
#

i did A0 row times B0 column -> A0 row times B1 column
same for A1

peak estuary
#

you need to take the rows of A and the columns of B

acoustic zealot
acoustic zealot
#

thats how i got to that result

peak estuary
#

from where are those 5 and 10 and 10

acoustic zealot
#

wait

peak estuary
#

did you use your wrong result for C?

acoustic zealot
#

A0,0 * (B0,0 + B1,0 + B2,0) + A0,1 * (B0,0 + B1,0 + B2,0) + A0,2 * (B0,0 + B1,0 + B2,0)
1 * (1 + 3+ 1) + 2 * (1 + 3+ 1) + 2 * (1 + 3+ 1) = 5 + 10 + 10

#

= C0,0 (in my solution)

peak estuary
#

no

#

each entry of A gets multiplied with one entry of B

#

A00*B00 + A01*B10+A02*B20

acoustic zealot
#

ah ok

acoustic zealot
peak estuary
#

yes

acoustic zealot
#

ok, so my result would be
(9 # 6
8 # 5)

peak estuary
#

yes

acoustic zealot
#

ok, thank you 🙂
i will practise a bit more

#

.close

safe radishBOT
#
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charred trench
#

The question:
Kenny is thinking of two numbers greater then 10.
He says: "The highest common factor (HCF) of my two numbers is 7"
"The lowest common multiple (LCM) of my two numbers is 84"

Write down the two numbers Kenny is thinking of.

What I want to know:
Short way to answer the question quickly and correctly using a venn diagram.

brave wolf
charred trench
#

Wait gonna do it

charred trench
brave wolf
#

okay, now the venn diagrams

#

each circle will represent one of the numbers and it will contains its prime factors

#

the intersection is gonna contain HCF

#

and the union is gonna contain factors of lcm

charred trench
brave wolf
#

oh sorry, GCD = HCF

#

greatest common divisor = highest common factor

charred trench
brave wolf
#

okay so we will start like this

brave wolf
#

both 2's must be in the same circle, because if they were in different circles, then we would have to put them to the intersection part

#

but the intersection part has to be only 7

charred trench
brave wolf
#

your left circle number is just 7

#

so you gotta move the 3 to the left circle

charred trench
brave wolf
#

i think you misunderstood what i meant

#

lcm is the all the factors in both circles

#

hcf consists of the factors in the intersection

#

first num consists of factors in left circle, 2nd num consists of factors in the second circle

#

so we start by placing 7 in the intersection (this part is obvious, 7 is in the HCF and HCF must be in the intersection)

charred trench
#

Im just wondering how the 3 came to the first number?

brave wolf
brave wolf
#

so you must move 3 to the first circle, to make the first number 7*3 = 21

charred trench
brave wolf
#

yep

charred trench
#

Ahh

brave wolf
# charred trench

if there wasnt the >10 condition, this would be also vaid solution

charred trench
#

So we got 21 and what would be the other how to work it out

brave wolf
#

corresponding to the numbers (7, 84)

brave wolf
#

second number is all the factors from the right circle

charred trench
#

So 2X2X7?

#

And that is 28

brave wolf
#

yep

charred trench
#

So the final answer is 21 and 28

#

Thanks.

brave wolf
#

np

charred trench
#

Shall I close now then?

brave wolf
#

hmm, @frozen veldt seems to be typing sth

charred trench
#

Yh rlly long

brave wolf
#

let's wait for a while

#

there is some caveats to this method, so i think he is going to point them out

frozen veldt
#

sorry

charred trench
#

.

frozen veldt
#

I have nothing worthwhile to add

charred trench
#

Right thats the caveats

frozen veldt
#

I just wrote my own solution

#

here it was

#

HCF = take the factors that are in both
LCM = take all the factors that are in both, with the highest power winning if they contain the same prime factor

we need both numbers to contain 7
we need both numbers combined to produce precisely 2, 2, 3 and 7

7 alone is not enough because it's not greater than 10

so maybe 7*2 works

now the second number has to have a 7 and a 3 but can't have a 2 so as to not contaminate the HCF

does 7*3 work? yes

but now the LCM doesn't work because we don't have enough twos, so we need

7*2*2 and 7*3 and that works because both are greater than 10

brave wolf
#

oh ic

charred trench
#

Its good gng

brave wolf
#

ill add the caveats myself then

#

Firstly, you must be careful not to do sth like this

#

do you know why this is wrong?

charred trench
brave wolf
#

but they cant be in the intersection, since that would make the HCF 7 * 2 * 2 instead

frozen veldt
#

I think a venn diagram is a weird way to visualize this

charred trench
brave wolf
#

so for example we cant draw a diagram like this

charred trench
brave wolf
#

the corrected version would look like this

#

Yes, but note that the other 2 stays there. You always take them in pairs

#

we take one 2 from the left circle and one 2 from the right and bring them to the middle as a single 2

#

and repeat this process until there are no 2 same factors

frozen veldt
#

nevermind I think a venn diagram is a good way to visualize this

charred trench
frozen veldt
#

because it's very easy to draw the diagram wrong

brave wolf
#

Yeah, similarly its easy to mess up the normal method too

#

if you arent used to it

charred trench
brave wolf
#

the only reason it feels weird to see the venn diagram for the first time is that we arent used to dealing with multisets

#

and thats exactly the same reason why the normal method may feel weird

frozen veldt
#

I don't know what the normal method is but if you just eyeball the gcd and the lcm then there's no way you'd get them wrong because reading the gcd and the lcm out of a prime factorization is something even a toddler can do

brave wolf
#

because reading the gcd and the lcm out of a prime factorization is something even a toddler can do
This is what i meant by the normal method lol

frozen veldt
#

I generally prefer guessing and checking in mathematics, works in a lot of cases like simple integrals

brave wolf
#

sure, but you gotta have intutition to guess effectively. and that intuition needs to be built somehow

charred trench
frozen veldt
#

I wouldn't call it intuition that the gcd is easier to visualize than the lcm

brave wolf
#

but your chances are improving after every round 🔥

frozen veldt
#

that's pretty much the first observation you make when you learn these things

#

so it makes sense to start with the gcd

#

and after that it's pretty straightforward to fill in whatever you need to satisfy the lcm

brave wolf
#

Well, I've seen a lot of interesting observations from my classmates

#

the only problem was 90% of them were wrong

#

but ig this is offtopic now

#

If you have no other questions, I think you can close this now @charred trench

charred trench
#

Alright

#

.close

safe radishBOT
#
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acoustic zealot
#

AES-Cryption:
could you correct my solution?
I mean, not if i there are misstakes, more if i generally did the correct steps

the green arrow are notes, i did while i was in the lecture. they have no connection to the current task

if the green highlighted number looks weird. i just did write 2B as a byte and bitshifted it.

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safe radishBOT
#

@noble spindle Has your question been resolved?

fathom adder
#

?

quasi timber
median vigil
#

.close

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exotic anvil
#

[This is a test]
Hallo can someone halp me with fractions they're very hard

karmic merlin
#

Sure, How can we help you

exotic anvil
#

.close

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hard crest
#

have u tried putting them in a blender that should soften them up

median vigil
light shoal
#

make them into a soup

tight nova
#

@exotic anvil why do you have three channels?

keen tulip
median vigil
#

it's not possible to open more than two channels

#

so idk what you're talking about

exotic anvil
exotic anvil
keen tulip
#

blud

tight nova
#

Oh*

median vigil
#

do you think obsidian counts the same as help channels

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tight nova
#

No

safe radishBOT
keen tulip
#

blud

tight nova
#

Oh shit

#

.close

keen tulip
#

.close

median vigil
#

.close

safe radishBOT
#
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#
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#
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keen tulip
#

wtf

median vigil
#

beautiful

rustic goblet
#

.close

tight nova
#

@rustic goblet hello!

rustic goblet
#

anyhow, you can open two channels if you do it in quick succession

#

but you can't open three

#

and the second will tell you off if you don't close the first one

tight nova
#

I meant lance has three channels with his name in them

rustic goblet
#

he had no such thing

#

only two

rustic goblet
#

obsidian doesn't count as a help channel Foxy_Hehe

tight nova
#

Ik

#

I'm only ever asking for help if #help-25 ever opens up

rustic goblet
#

why 25 specifically?

safe radishBOT
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tight nova
tight nova
#

.close

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#
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still grove
#

I understand that the max value is (1,2) and no points of inflection. Should the min value be (3,-2)? The answer key doesn't have any min value so I was wondering if it is a mistake or there really is no min value

stoic dune
#

f is continuous on [0,3]. Reconsider your graph

#

If f is only defined on [0,3], then you're correct about the min

still grove
#

would it look smth like this?

stoic dune
#

Yeah that looks good!

still grove
#

okayyy, thanks!

#

.close

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long galleon
#

So, some say dozenal is a better way to count, others seximal! Those who dare even more say binary is the best way to count. But, what if we've got it all wrong, and there's a better way to maths (maths as a verb like in Toki Pona) that isn't counting? Even if there isn't a better way than what we have now, what might alternatives look like? What I'm circling around, if the above wasn't a good enough description, is the primitive system. Not foundational/axioms. If there is no alternative either, or if this is just too hard to answer, then that's an answer too.

still stone
#

all number systems are kinda arbitary

#

i think

long galleon
#

I've thought about this a lot myself and personally have settled on binary though I'm not really asking about bases or looking to debate, sorry.

open wedge
#

Two line summary

quasi bison
#

so wait hold on, what are you looking for a better way to do, exactly?

open wedge
#
  1. Human: base 10
  2. Computers: base 2
long galleon
#

Is counting the only way to primitively represent math?

quasi bison
#

not a numeration system, and not axioms, but what

#

what do you mean by "primitively represent math"

still stone
#

no one counts after learning algebra

open wedge
flat frigateBOT
#

1 divided by 0 equals Infinity

long galleon
still stone
#

your question is a bit vague

long galleon
#

Prety much is there an alternative to counting.

still stone
#

?? multiplication??

quasi bison
#

an alternative to what end

long galleon
#

There's a lot of debate about how to count with bases and stuff but I'm just asking if the idea which this is based on is wrong.

#

Answers too could just be that no there isn't an alternative or this question can't be answered.

quasi bison
#

i think that nobody here understands what you're talking about or what kind of "alternative" you are even envisioning.

#

and when i say "nobody here", i mean "maybe not even yourself".

long galleon
#

Yeah

long galleon
long galleon
quasi bison
#

ok and how are you going to get any sort of economic task done if numbers in any way, shape or form are out of the picture?

long galleon
long galleon
austere goblet
#

!done?

safe radishBOT
#

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

long galleon
#

Just one minute

#

I have something which I'm evaluating real quick

#

I can think of ranges but those still rely on counting numbers to a degree even if they're quantized. Order can't be done either without in some way representing the value that ties back to coutning numbers. Geometry could be used but it's just a roundabout way of replacing counting numbers while sitll having the same fundemental idea. Permutations like in group theory honestly maybe could contend but that's for me to look into and would answer the question, though not sure about this once since I am not familiar with group theory really.

#

At most I can think of parity (valid contender!), but parity alone is way too basic to get any modern maths done.

safe radishBOT
#

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long galleon
#

.close

safe radishBOT
#
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long galleon
# quasi bison ok and how are you going to get any sort of economic task done if ***numbers in ...

This was probably the dumbest interaction you've had all day, though if you were curious, the question which I was trying to ask (I have poor skills with articulating myself after the brain damage /srs) is if an alternative day to day representation of logic and all stuff math is regularly needed for existed or could meaningfully be conceived of. The answer is no, not really unless you want something extremely cumbersome. This has been in my head for several weeks.

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halcyon light
safe radishBOT
halcyon light
#

can someone clue me in on what to do after

safe radishBOT
#

@halcyon light Has your question been resolved?

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acoustic zealot
#

Prove through Induction:

Am I missing something.
How do i prove this

cunning shard
#

yeah, it looks correct.

#

gut gemacht.

acoustic zealot
#

Wait

#

Thats the proof?

cunning shard
#

proof.

#

You basically, showed this

  1. P(0) is true.

  2. P(n) is true => P(n+1) is true.

so, since P(0) is shown to be true, it follows by (2), P(1) is true,

i.e., you get a chain of true statements, P(0), P(1), P(2),..., where the truthness is implied as follows,

P(0) => P(1) => P(2) => ....

acoustic zealot
#

Ah ok, i thought i have to get back to n(n+1)

#

Ok thanks

#

.close

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cloud maple
#

I think there's something wrong with this problem but I'm not quite sure what is it

cloud maple
#

Progress

#

I think equality is attained when (a,b,c) = (0,1,1) and its permutations

safe radishBOT
#

@cloud maple Has your question been resolved?

cloud maple
#

<@&286206848099549185> hi

idle aspen
#

kiểu

#

<=> a2 ≥ 0 sẵn rồi ý

cloud maple
#

Tui thấy ngược dấu á

#

b^2+c^2≥2bc≥2

#

Bên trên thì lại có bc≤1

idle aspen
#

bc≤1 ?

cloud maple
#

1 ≥ b^2c^2(b^2-bc+c^2) ≥ b^3c^3

idle aspen
#

1 ≥ b^3c^3 với mọi b,c dương

#

okay ill leave this to an english helper

#

minimise question

cloud maple
#

okay

idle aspen
#

@hel

#

<@&286206848099549185>

cosmic vine
idle aspen
cosmic vine
#

I can't read

cosmic vine
#

I don't know that lauguge

cloud maple
#

that is english bro wtf

compact lodge
#

lmao what 😭💔

cloud maple
#

Wait nvm

#

My inequality is wrong

#

The equivalent inequality is not actually equivalent 😭

#

.close

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#
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opaque fern
#

\lm this is kind of a weird question but what do the coordinates entail here? Like, do we say [
s_1: (\varphi_1(t), \varphi_2(t)) = (-\alpha, \alpha)?
]
that don't make much sense tho idk

flat frigateBOT
opaque fern
#

\lm $\varphi_1$ and $\varphi_2$ are meant to be basis functions that you can construct any function in that system with. So in the above case you would have [
s_1(t) = -\alpha\varphi_1(t) +\alpha\varphi_2(t)
]

flat frigateBOT
opaque fern
safe radishBOT
#

@opaque fern Has your question been resolved?

dark elm
#

We have $f:\mathbb{R}^{2}\mapsto \text{Set of some functions}$ defined by
$$f((x,y))=x\varphi_{1}(t)+y\varphi_{2}(t)$$
If we let $p_{1}=(-\alpha,\alpha)$, we get:
$$f(p_{1})=s_{1}$$

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flat frigateBOT
#

BBMaths

safe radishBOT
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thin lion
safe radishBOT
thin lion
#

Hi is this rigorous enough for this?

verbal cloud
#

I would say yes

thin lion
#

alright tysm

#

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thin lion
#

Hello! Im back again

safe radishBOT
thin lion
#

I feel like with other parts of real analsyis, it all feels very rigorosu when writng but idk with series

#

like is this wht someone marking wants me to realise?

proud tree
thin lion
#

😭 oh waitttt

#

no

#

scrap that

#

lemme redo that

vague zinc
# thin lion

You could even make the first one less rigorous 😉 Notice the geometric series with 8/25 < 1

vague zinc
# thin lion wdym here

Well it's obviously not wrong, just unnecessary to use the root test once you've reduced it to a geometric series already

thin lion
thin lion
#

Could have just evaluated the geometric series tbh

thin lion
#

wait i do use root test for this right?

#

just cause of the 2^n

vague zinc
#

Have you learned ratio test (d'Alembert)

thin lion
#

ohhhhhhhhhhh

#

😭 yea

#

Is that the way?

vague zinc
#

That's the ratio test

#

And see if its <1

thin lion
#

oh wait yes sorry

#

u get 1/2 < 1 ?

#

so converges?

vague zinc
#

Yep

#

abs convergence

thin lion
#

ah i see

vague zinc
#

It's like 4 lines to prove its convergence

thin lion
#

yea i overthought it

#

not sure why i decided to randomly do comparison test in the middle of ratio test

#

alr tysm

#

.close

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#
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topaz furnace
#

i need someone help me explain this really fast

topaz furnace
#

when loga(b)=x, why a has to be greater than 0

brave wolf
topaz furnace
#

just started logarithm so kinda confused

brave wolf
#

it would be the inverse of (-2)^x

fathom adder
#

Because it means ln(b)/ln(a) = x

brave wolf
topaz furnace
#

i havent learnt about ln

topaz furnace
brave wolf
#

but (-2)^1/2 isnt even defined (you cant have square root of negative numbers)

#

who knows what (-2)^pi would be

topaz furnace
#

oh yeahhh, but some work, while some dont, why we have to conclude that a>0

brave wolf
#

(-2)^(28/81), which is very close to 1/3 would be around cbrt(2), which has opposite sign to (-2)^(1/3)

brave wolf
#

(-2)^x behaves so weirdly that we dont really want an inverse of that

topaz furnace
#

im still very confused 😵‍💫

brave wolf
#

my point is that $\log_{-2}{x}$ would be an inverse of $(-2)^x$

flat frigateBOT
#

MathIsAlwaysRight

brave wolf
#

and (-2)^x behaves very badly

#

,calc (-2)^0.5

flat frigateBOT
#

Result:

1.4142135623731i
brave wolf
#

okay ignore this, its wrong

topaz furnace
#

i thought that log-2(x) is that (-2)^n=x, why it is an inverse of (-2)^x

brave wolf
topaz furnace
#

new to me

brave wolf
#

dont worry about it then

#

its just the fact that log_(-2)(x) depends on (-2)^x, which behaves very badly

#

so if we defined log_(-2)(x), it would also behave very badly

#

so we dont even bother defining it

#

this is how badly it behaves

#

undefined, a little bit further around -1.4 and another bit further its around 1.47

topaz furnace
#

ohhhh no way

#

might explode

#

understand better now catthumbsup

#

by the way

topaz furnace
brave wolf
topaz furnace
#

oh coollll

brave wolf
#

it works by putting $ $ around your equations

#

and the equations have to be written in special syntax

#

for example fractions are done using $\frac{1}{2}$, logs with $\log{x}$, $\sqrt{\text{or u can do square roots}}$

flat frigateBOT
#

MathIsAlwaysRight

topaz furnace
#

ohhhhh complicated

#

thanks for your timeee, im going to try it out, appreciate it a lot

brave wolf
#

np

topaz furnace
#

🔥

#

.close

safe radishBOT
#
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safe radishBOT
#
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steep magnet
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steep magnet
#

I got the right formula but I was just kinda guessing

#

I kinda knew that s = ln(t) and t = 1 and t = 2 would be bounds, not really sure why tho

light shoal
#

isn't $\int_0^{\ln t}$ going to get you the region below the curve $s = \ln t$?

steep magnet
#

I also guessed that the missing bound would be 0, not sure why either

flat frigateBOT
steep magnet
#

Heres the full solution

steep magnet
steep magnet
#

Cause I got lucky with my answer but I want to understand what im actually doing

vague zinc
#

s is horizontal and t is vertical. You should start out by rewriting the curve to t = ...

steep magnet
#

I dont know what were doing

vague zinc
#

Just easier to interpret what 'above the curve' actually means if you rewrite them

steep magnet
#

Interpret it how sry

vague zinc
#

Well, it's harder to picture 'above' when the curve is written as s = ln t because 'above' normally refers to the vertical direction

#

That's why we rewrite to t = e^s

#

(It's easy to picure that you want t >= e^s)

steep magnet
#

Im so confused 😭

#

Ok i think im just going to try and find another video on this topic

#

.close

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#
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steep magnet
#

If anyone has a good video pls ping me and send it

safe radishBOT
#
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eager junco
#

Hi, can someone explain to me how Rodrigues rotation formula works? Thanks

quasi bison
#

In the theory of three-dimensional rotation, Rodrigues' rotation formula, named after Olinde Rodrigues, is an efficient algorithm for rotating a vector in space, given an axis and angle of rotation. By extension, this can be used to transform all three basis vectors to compute a rotation matrix in SO(3), the group of all rotation matrices, from ...

#

this one? @eager junco

safe radishBOT
#

@eager junco Has your question been resolved?

eager junco
#

Yes

safe radishBOT
#
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eager junco
#

.reopen

safe radishBOT
eager junco
quasi bison
#

did you read the wikipedia article at least

eager junco
#

Yes I did read it

#

But it just looks like magic

quasi bison
#

do you understand up to the point where v is decomposed into a component parallel to k and a component perpendicular to k

eager junco
#

What’s before that?

#

I know that the cross product gives one of the two perpendicular vectors

quasi bison
#

bad transparent copy-paste

#

this picture. do you understand the idea here y/n

eager junco
#

Is v rot the answer we are trying to get?

quasi bison
#

yes

eager junco
#

Ok, what about w?

quasi bison
#

$\bd{k}$ and $\bd{v}_{\perp}$ are perpendicular (by construction); $\bd{w}$ is perpendicular to them both (also by construction) and completes an orthogonal triad (because we want that to happen)

flat frigateBOT
eager junco
#

Oh so is it v perpendicular cross v parallel?

quasi bison
#

v_perp crossed with k rather than with v_parallel.

#

that way $|\bd{w}| = |\bd{v}_{\perp}|$.

flat frigateBOT
quasi bison
#

(but crossing with v_parallel would give the same direction)

eager junco
#

Oh I see

#

So v parallel + v perpendicular = v?

#

I think I understand diagram now

#

@quasi bison may i know how these vectors are calculated?

quasi bison
#

thats what it means to decompose v into a perp and parallel component relative to k

eager junco
#

Got it

quasi bison
#
roughly speaking the recipe goes as follows:
\begin{enumerate}
  \item calculate $\bd{v}_{\parallel}$ by projecting $\bd{v}$ onto $\bd{k}$ (via dot products)
  \item calculate $\bd{v}_{\perp}$ as $\bd{v} - \bd{v}_{\parallel}$ (or via cross-product shenanigans as wikipedia gives)
  \item calculate $\bd{w}$ as $\bd{v}_{\perp} \times \bd{k}$ --- a vector of the same length but rotated 90 degrees in the direction of rotation specified by $\bd{k}$
  \item rotate $\bd{v}_{\perp}$ by angle $\theta$ in the plane spanned by $\bd{v}_{\perp}$ and $\bd{w}$
  \item add $\bd{v}_{\parallel}$ back in
  \item ???
  \item profit
\end{enumerate}
flat frigateBOT
eager junco
#

Ok, according to the wiki, it says that v parallel = (v dot k)k

#

May I know which multiplication it is implying here?

#

Oh, nvm I forgot that do product returned a scalar

eager junco
quasi bison
quasi bison
eager junco
#

Stuck at step 4

eager junco
#

What does span mean?

quasi bison
eager junco
#

I think it’s by using matrix multiplication

eager junco
quasi bison
#

ehhhhhh

#

overkill.

quasi bison
#

though maybe it's best that you brush up on your linalg.

eager junco
quasi bison
#

not very, imo

#

it'll be a bit of a bash/slog but not like... terribly difficult once you grasp rotations in 2d and linear maps in general

eager junco
#

Got it thank you so much for your help!

#

.close

safe radishBOT
#
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eager junco
#

Have a good day 🙂

safe radishBOT
#
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fervent granite
#

We know that we can use summation for approximating areas under a curve $\f(x)$ by partitioning the area into rectangles of equal width deltax and the height defined as $\f(x_i)$, where $x_i$ is our endpoint (suppose right endpoint), $i$ is our index, and $i=1$. We do this for $n$ subdivisions, and the evaluation of our sum tends to the true area under the curve as $n$ is set to larger and larger integer values. In fact, we can evaluate the limit as $n\rightarrow\infty$ of this sum to find the exact area under the curve, leading to the integral.
We turn our attention now to the product. What can we do to find geometric purpose with the product?

tardy mango
fervent granite
#

Ah I do see the product with expression 1+f(x_i)deltax. My problem arises from the idea of geometrically drawing this. I understand that this is not an expression of area, but that’s where my capacity of grasping the expression stops. How would I go about drawing this, as is possible with drawing Riemann sums?

#

It would be one thing to just accept the expression, but I want a geometric motive for it that I can see on paper.

#

<@&286206848099549185>

#

<@&286206848099549185>

#

<@&286206848099549185>

safe radishBOT
#

@fervent granite Has your question been resolved?

dark elm
#

If you have questions about it, I think more people might help

safe radishBOT
#

@fervent granite Has your question been resolved?

safe radishBOT
#

@fervent granite Has your question been resolved?

safe radishBOT
#

@fervent granite Has your question been resolved?

open wedge
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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.

open wedge
#

stop spamming helpers

fervent granite
#

.close

safe radishBOT
#
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safe radishBOT
#
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trim lion
#

From the top of a 12m high building, the angle of elevation of the top
of a cable tower is 60° and the angle of depression of its foot is 45°.
Determine the height of the tower

Guys I'm having problems visualising this and making a diagram which is important to do in the exam I need help in how you visualise this and also how to solve it

limpid lodge
trim lion
limpid lodge
#

Depression is when you're looking down from a point

trim lion
#

Oh

#

And elevation

limpid lodge
#

Elevation would be when you're looking up

trim lion
#

If i were to make a diagram of this question how will i?

limpid lodge
#

Start with a vertical line for the building

trim lion
#

Will it be smth like this

trim lion
#

Okay

#

Okay i understand it now thank you for the help

#

I'm closing now

#

.close

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#
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safe radishBOT
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safe radishBOT
covert talon
#

What next

brave wolf
#

you didnt divide the 7

covert talon
#

It’s a plus

#

Oops

#

My handwriting

quasi bison
#

is it handwriting or finger-writing

#

or mouse-writing

safe radishBOT
#
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covert talon
quasi bison
#

💀

#

!msgdel

safe radishBOT
#

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quasi bison
covert talon
#

its cus im doing it on my apple pencil but for some reason it has some like autowrite thing

#

like it changes what i write

quasi bison
#

go open a new channel

covert talon
#

ok

#

.close

pure agate
#

Looks like a test.

covert talon
#

its a past paper

#

:p

safe radishBOT
#
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cloud maple
safe radishBOT
cloud maple
#

(Given a,b,c be non-negative real numbers such that ab+bc+ca > 0, prove the above inequality)

#

I instantly thought of using pqr method when looking at this, and the inequality also allows me to consider p = 1

#

But I still can't think of a way to work it out, especially the (1+√2)^2

cloud maple
#

Let p = a+b+c, q = ab+bc+ca and r = abc

#

Substituting (ka,kb,kc) into the inequality and it still holds, so we just need to consider p = a+b+c = 1

faint seal
#

Yeah it’s homogeneous

#

The last term seems to be the most problematic

cloud maple
#

Yea

faint seal
#

Where is this problem from?

open wedge
#

-# t ngu bđt lm

cloud maple
cloud maple
#

No way you can pull out the (1+√2) just using known inequalities

faint seal
#

Maybe you define a function and then find that its minimum value is (1+sqrt2)^2

cloud maple
#

Well there's this inequality which can help in defining a function

#

except its

too long

#

Also one more note: the equality is attained if a = b = c, yes, but there's one more case and thats the main reason (1+√2) appears

faint seal
#

[ \frac{(a^2+b^2+c^2)\left[(a-b)^2+(b-c)^2+(c-a)^2\right]}{2(ab+bc+ca)(a+b+c)^2} \ge \frac{(1+\sqrt{2})^2(a-b)^2(b-c)^2(c-a)^2}{(a+b)^2(b+c)^2(c+a)^2} ]

flat frigateBOT
#

kheer257

faint seal
safe radishBOT
#

@cloud maple Has your question been resolved?

safe radishBOT
#

@cloud maple Has your question been resolved?

safe radishBOT
#

@cloud maple Has your question been resolved?

safe radishBOT
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#
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opaque fern